A plurality of radially arranged hammers each having a radially outer end are driven to undergo pivotal movement around their outer ends between front operating and rear rest positions. A first yoke member faces the radially arranged hammers, and has a plurality of cores opposed to the corresponding hammers and a dependent portion depending laterally from an outer periphery of the first yoke member to be magnetically coupled to the outer ends of the hammers. A plurality of coils are wound around respective ones of the cores to magnetically drive the corresponding hammers. A second yoke member has an outer periphery magnetically coupled to the dependent portion of the first yoke member and a plurality of tongues extending radially inwardly to define a plurality of slots between adjacent tongues to receive therein the hammers. A press spring acts on the respective outer ends of the hammers to urge the same pivotably against the dependent portion of the first yoke member to position the respective outer ends of the hammers in place relative to the dependent portion of the first yoke member. A plurality of printing elements are actuated by the respective hammers when driven to the front operating position for printing marks on a printing medium.