A hammer with simplified structure and reduced costs that maintains its capability as a mass body to impart a touch weight. The hammer is configured such that it is possible to fix the two mass plates to the metal base plate by means of a single rivet. Therefore, the number of places in which the rivet holes are drilled and disposed in both mass plates and the metal base plate are kept to a minimum, and it is possible to limit the lightening of the weight of both mass plates and the metal base plate by that amount. As a result, since it is possible to configure the base plates and the metal base plate with smaller dimensions while maintaining the required weight, the capability as a mass body to impart a touch weight can be maintained while preventing the enlarging of the hammer overall.