1. A medical image display apparatus which displays, in a display screen, a display image having undergone gray level transform that is changing number of gray levels of a medical image, the apparatus comprising: an obtaining unit configured to obtain a representative value of pixel values concerning a region of a block, in the medical image, which corresponds to each partial region in a region designated in the display image; a setting unit configured to set a specific region in the display screen so as to include the designated region; and a display control unit configured to superimpose/display and arrange representative values obtained by the obtaining unit on the specific region in correspondence with an arrangement of the partial regions.