To provide a turbine and a gas turbine of high efficient, small size, light weight and reduced cost, by decreasing an energy loss of operating fluid.

In a turbine and a gas turbine, a stator 3 is fixedly supported in a turbine housing 2 provided with injection nozzles 2a, 2a', a turbine rotor 5 is arranged to be opposed to the stator, a high speed swirl flow of operating fluid is generated in a radial surface of the stator, and this swirl flow is applied to directly act in a radial surface of the turbine rotor, so as to drive the turbine rotor rotated by high torque at a low speed.