A frequency converter includes: a primary winding 12 in which a plurality of windings on which a polyphase alternating voltage is applied are arranged periodically along a particular direction; a secondary winding 22 which is magnetically coupled to the primary winding 12 and in which a plurality of windings are arranged along the particular direction with a repetition period different from the primary winding 12; and a frequency modulation part 3 which is arranged on a magnetic path between the primary winding 12 and the secondary winding 22 and in which a plurality of magnetic materials 31 are arranged periodically. Then, the pitch of the plurality of magnetic materials 31 and the winding arrangement period of the primary winding 12 and the secondary winding 22 are different from each other so that an alternating voltage having a frequency different from the frequency of the polyphase alternating voltage is induced in the secondary winding 22.