A squirrel-cage rotor including a rotor which has a plurality of rotor slots on an outer circumferential portion thereof and in which secondary conductors accommodated in the rotor slots rotate freely inside a stator as a result of interaction with a rotating magnetic field formed by the stator. The plurality of rotor slots has the same shape and size, and an arrangement spacing thereof with respect to the rotation direction of the rotor is made uneven within a slot uneven arrangement period (360/(a))° obtained by equally dividing one rotation period of the rotor by a divisor (a) of a number p of poles in the stator.