An immunity-inducing agent comprising as an effective ingredient a specific polypeptide is disclosed. These polypeptides were isolated, by the SEREX method using a cDNA library derived from canine testis and serum from a cancer-bearing dog, as a polypeptide which binds to an antibody existing specifically in serum derived from a cancer-bearing living body. The polypeptides can induce immunity in a living body and cause regression of a tumor in a cancer-bearing living body. Therefore, these polypeptides are especially effective as a therapeutic and/or prophylactic agent for a cancer(s).
