A medical image display apparatus has a dividing unit and a setting unit. The dividing unit divides a range after changing to an overlapping range that a range after changing overlaps a range before changing, and a non-overlapping range that not includes the overlapping range, when a position of the range is changed. The setting unit configured to set a pixel value after changing based on a pixel value constituting a diagnostic image before changing and voxel values along a predefined direction in the non-overlapping range according to a predefined condition about a pixel that a position of a voxel value in volume data corresponding to the pixel value constituting the diagnostic image before changing exists in the overlapping range, among each pixels constituting a diagnostic image after changing generated based on the voxel values along the predefined direction in the range after changing.