1. A medical image display device comprising, a region of interest setter for setting a first region of interest being a region of an observation site in volume data, and a second region of interest being a lesion candidate region relating to the observation site, a display image generator for generating a display image that allows a size of an adjacent second region of interest to be distinguishable, being the second region of interest adjacent to the first region of interest on a projection line of interest, when a pixel having a reference pixel value on the projection line of interest corresponds to a pixel of the first region of interest, and a display unit for displaying the display image.