The present invention provides a method for producing a peptide for the treatment (in particular, immunotherapy), monitoring, or diagnosis of a disease in a subject. This method is achieved by obtaining information pertaining to a genome read, for example an exome read, of the subject and a mutation thereof, and, as necessary, information regarding the RNA sequence of the subject and information regarding the MHC type of the subject, analyzing an epitope related to the mutation on the basis of the information pertaining to the genome read (for example, the exome read) and the mutation, arbitrary information from the RNA sequence, the MHC type information, and information regarding the disease, and producing a peptide, as necessary, on the basis of information regarding the epitope.