Under a condition that rotor rotation speeds ωes are equal, winding wire currents Id, Iq are equal, and winding wire inductances Ld, Lq are equal in first and second electric motors (1, 2), a magnet temperature anomaly detector (30) provided in a microcomputer (5) calculates a change ratio d(|Φml−Φmr|)/dt of a magnetic flux difference between the first and second electric motors (1, 2) based on the difference Vql*−Vqr* between a q-axis voltage command value Vql* corresponding to the first electric motor (1) and a q-axis voltage command value Vqr corresponding to the second electric motor (2), and then when the change ratio d(|Φml−Φmr|)/dt of the magnetic flux difference is more than a predetermined threshold Sh1, it is determined that a permanent magnet of at least any one of the electric motors (1, 2) has a temperature anomaly.