A discriminator includes a common learning unit and a plurality of learning units that are connected to an output unit of the common learning unit. The discriminator is trained, using a plurality of data sets of a medical image and an image data of a first disease region, such that information indicating the first disease region is output from a first learning unit in a case in which the medical image is input to the common learning unit. The discriminator is trained, using a plurality of data sets of a medical image and an image data of a second disease region having at least one of a medical causal relationship or an anatomic causal relationship with the first disease, such that information indicating the second disease region is output from a second learning unit in a case in which the medical image is input to the common learning unit.