A medical simulation apparatus is provided, which is capable of performing a simulation by correlating a three-dimensional image with an entity model.Coordinates of measurement marks MP1, MP2, MP3 on a surface of a lower dental arch model 62 in a coordinate system defined by three reference marks MK1, MK2, MK3 are acquired before and after displacement of the lower dental arch model 62. The coordinates thus acquired are converted into coordinates in a coordinate system defined by reference marks PK1, PK2, PK3 on the basis of a relationship between the reference marks MK1, MK2, MK3 and the reference marks PK1, PK2, PK3. Then, changes in the coordinates after displacement of the lower dental arch model 62 are determined, and a region preliminarily specified in a three-dimensional image displayed on a display 5 is displaced on the basis of the coordinate changes thus determined.