A power plant that is capable of attaining downsizing and reduction of manufacturing costs and enhancing the degree of freedom in design thereof. In the power plant 1, a first rotating machine 11 includes a first rotor 14 having a predetermined plurality of magnetic poles 14a, a stator 13 that generates a predetermined plurality of armature magnetic poles to thereby generate a rotating magnetic field, and a second rotor 15 having a predetermined plurality of soft magnetic material elements 15a. The ratio between the number of the armature magnetic poles, the number of the magnetic poles, and the number of the soft magnetic material elements is set to 1:m:(1+m)/2 (m≠1.0). One of the rotors 14 and 15 is mechanically connected to an output portion 3a of a heat engine 3, and the other of the rotors 14 and 15 and a rotor 23 of a second rotating machine 21 are mechanically connected to driven parts DW and DW. Further, in starting the heat engine 3, when the rotational speed of the output portion 3a is not lower than a first predetermined value NEST1, the heat engine 3 is started in a state where the rotational speed of the output portion 3a is not increased.