For the purpose of preventing resin from flowing into a commutator when resin molding a rotor, a rotor for a flat coreless motor comprises a printed wiring board, on one side of which a plurality of air-cored armature coils are provided, and on the other side of which a plurality of segment patterns constituting a commutator and a wiring pattern are provided. These members are molded with resin into a unitary body with the segment patterns exposed. Wiring pattern parts are provided so as to surround the outer periphery of the commutator.