diff --git a/core/renderer.py b/core/renderer.py
index 2bbca5c..6709e74 100644
--- a/core/renderer.py
+++ b/core/renderer.py
@@ -165,8 +165,44 @@ class ExcelRenderer:
         
         # Draw background and border
         # Scale border width: at least 1px, roughly 1px per scale unit but kept thin for aesthetics
-        border_width = max(1, scale) 
-        draw.rectangle([x1, y1, x2, y2], fill=bg_color, outline=(200, 200, 200), width=border_width)
+        default_border_width = max(1, scale)
+        
+        # Draw background
+        draw.rectangle([x1, y1, x2, y2], fill=bg_color)
+        
+        # Handle borders
+        # Default thin grey border if no specific border is set (or for gridlines)
+        # Note: OpenPyXL borders are complex. We'll simplify: check each side.
+        
+        border_color = (200, 200, 200) # Default gridline color
+        
+        if cell.border:
+            # Helper to draw a side
+            def draw_side(side_obj, coords):
+                if side_obj and side_obj.style:
+                    # Parse color if available, else default black for set borders
+                    b_color = (0, 0, 0)
+                    if side_obj.color:
+                        b_color = self._parse_color(side_obj.color, default=(0, 0, 0))
+                    
+                    # Determine width based on style
+                    # 'thin', 'medium', 'thick', 'double', 'hair', 'dashed', 'dotted'
+                    width = default_border_width
+                    if side_obj.style in ['medium', 'thick', 'double']:
+                        width = default_border_width * 2
+                    
+                    draw.line(coords, fill=b_color, width=width)
+                else:
+                    # Draw default gridline
+                    draw.line(coords, fill=border_color, width=default_border_width)
+
+            draw_side(cell.border.left, [x1, y1, x1, y2])
+            draw_side(cell.border.right, [x2, y1, x2, y2])
+            draw_side(cell.border.top, [x1, y1, x2, y1])
+            draw_side(cell.border.bottom, [x1, y2, x2, y2])
+        else:
+            # Fallback to simple rectangle outline
+            draw.rectangle([x1, y1, x2, y2], outline=border_color, width=default_border_width)
 
         # Content
         cell_value = cell.value
diff --git a/tests/test_border.py b/tests/test_border.py
new file mode 100644
index 0000000..305e44d
--- /dev/null
+++ b/tests/test_border.py
@@ -0,0 +1,36 @@
+import pytest
+import io
+import os
+from core.renderer import ExcelRenderer
+from PIL import Image
+
+# Use the file provided by the user for reproduction
+TEST_FILE_PATH = "tests/kshj_gt1767081783800.xlsx"
+
+@pytest.mark.skipif(not os.path.exists(TEST_FILE_PATH), reason="Test file not found")
+def test_border_rendering_real_file():
+    """
+    Test rendering with a real file that has border issues.
+    This test will generate an output image for visual inspection.
+    """
+    with open(TEST_FILE_PATH, "rb") as f:
+        content = f.read()
+    
+    renderer = ExcelRenderer(content)
+    
+    try:
+        # Render with high DPI scale
+        img_bytes = renderer.render_to_bytes(scale=3)
+        
+        # Save for visual inspection
+        output_path = "tests/test_output_border.png"
+        with open(output_path, "wb") as f_out:
+            f_out.write(img_bytes)
+            
+        print(f"Generated test image at: {os.path.abspath(output_path)}")
+        
+        assert isinstance(img_bytes, bytes)
+        assert len(img_bytes) > 0
+        
+    except Exception as e:
+        pytest.fail(f"Rendering failed: {e}")