1. A medical image compression device comprising: a compression target obtaining unit configured to obtain (i) a target image which is a medical image to be compressed and (ii) diagnostic finding information for the target image; a clinical condition range obtaining unit configured to divide the target image into regions each corresponding to a different one of clinical conditions based on the diagnostic finding information; a pixel value prediction unit configured to, for an arbitrary pixel, refer to a prediction knowledge database in which an appearance distribution of a pixel value of an arbitrary pixel is stored for each of the clinical conditions, and calculate a prediction probability of a pixel value of a prediction target pixel based on the clinical condition of the prediction target pixel and the appearance distribution of the pixel value of the prediction target pixel, the appearance distribution of the pixel value of the arbitrary pixel corresponding to a pixel value included in a predetermined neighboring range; a coding unit configured to code the pixel value of the prediction target pixel based on the prediction probability of the pixel value calculated by the pixel value prediction unit; and an output unit configured to output a code of the prediction target pixel after being coded by the coding unit.