The synchronous motor includes a rotor including a rotor core constituted of segment poles disposed in a ring and a stator including a stator core disposed radially outward or inward of the rotor with a gap therebetween and a multiple-phase stator winding wound on the stator core. Each of the segment poles has a magnetic salient pole characteristic. The rotor is rotated in synchronization with a rotating magnetic field generated when the multiple-phase stator winding is applied with a multiple-phase AC voltage. The lamination thickness as an axial length of the stator core is shorter than the lamination thickness as an axial length of the rotor core.