An object of the invention is to provide an armature of an electric motor that provides a maximum of space for winding without causing an increase of the magnetic resistance and reduction of the coil space factor. The armature of the electric motor includes a stator yoke 5 of a stator core 1 wherein a plurality of the stator cores 1 forms a substantially annular shape; and a film insulator 4 formed corresponding to a tooth 6 and a stator yoke 5 of the tooth 6, shoes 2b and 3b being provided at locations corresponding to both side ends of a front portion of a protrusion 6a of the tooth 6, the film insulator 4 being fittingly fixed to grooves 2c and 3c by its being sandwiched between a connection-side insulator 2 and an opposite-side-of-connection insulator 3, the insulators 2 and 3 having grooves 2c and 3c at roots of the shoes 2b and 3b, respectively, along both side ends 6b of the front portion of the tooth 6.