Provided are a composite image generating apparatus, a composite image generating method, a composite image generating program for obtaining a composite image having a user's desired impression. A first mount image 51 is determined on the basis of an impression value along a first impression axis, with respect to a composite target image 50. The composite target image 50 and the first mount image 51 are combined to obtain a first composite image Sy1. A user moves a slider 63 of a first desired impression value designating slider axis 62 corresponding to the first impression axis to designate an unspecified desired impression value. A second mount image having the designated desired impression value is determined, the second mount image, instead of the first mount image 51, and the composite target image 50 are combined to obtain a second composite image having the user's desired impression.