A power plant capable of reducing loss in a fluid passage switching mechanism and enhancing robustness of the power plant. When a second member 33e is in a first position with respect to a first member 33d, a first communication port pp communicating with a fluid pressure supply source 14 and second and third communication ports pm1 and pm2 communicating with first and second pressure chambers 13b and 13c of a fluid pressure motor 13, respectively, communicate, and the second and third communication ports pm1 and pm2 are shut off from a fourth communication port pr connected to a reservoir 31. When the second member is in a second position, the first and second communication ports communicate, the first and third communication ports are shut off from each other, the second and fourth communication ports are shut off from each other, and the third and fourth communication ports communicate. When the second member is in a third position, the first and second communication ports are shut off from each other, the first and third communication ports communicate, the second and fourth communication ports communicate, and the third and fourth communication ports are shut off from each other. The first to fourth communication ports are provided in a plurality of communication port groups each formed by the first to fourth communication ports.