A power plant which is capable of enhancing the driving efficiency and the power-generating efficiency thereof. In the power plant 1, the output shaft 3a of a heat engine 3 is connected to driven parts DW and DW via a first transmission 20. A rotating machine 31 includes a first rotor 34 having a magnetic pole row that has each two adjacent magnetic poles 34a so disposed as to have polarities different from each other, a stator 33 having an armature row that is disposed in a manner opposed to the magnetic pole row, for generating a rotating magnetic field between the armature row and the magnetic pole row by a predetermined plurality of armature magnetic poles, and a second rotor 35 having a soft magnetic material element row that is formed by a plurality of soft magnetic material elements 35a arranged in a manner spaced from each other, and is disposed between the magnetic pole row and the armature row. The ratio between the number of the armature magnetic poles, the number of the magnetic poles 34a, and the number of the soft magnetic material elements 35a is set to 1:m:(1+m)/2 (m≠1.0). One of the first and second rotors 34 and 35 is connected to the output shaft 3a of the heat engine 3, and the other thereof is connected to the driven parts DW and DW.