The present invention makes it possible to display a maximum intensity projection image with high image quality in a short processing time when performing movement, enlargement, reduction and rotation display of the maximum intensity projection image, even when using a PC with a low processing capacity. The present invention proposes an image processing apparatus for rendering a maximum intensity projection image by extracting, as objects to be rendered, only voxels having a high brightness value in three-dimensional volume data and using the brightness values of these voxels for the corresponding pixels.
