An expansion turbine including a turbine housing, a plurality of variable nozzles inside the turbine housing at intervals in a circumferential direction of the expansion turbine, the variable nozzles being configured to be rotatable about a rotation shaft, and a turbine wheel disposed rotatably inside the turbine housing, the turbine wheel including a plurality of turbine blades disposed downstream of the variable nozzles. The turbine housing has a first wall surface which faces tips of the turbine blades, and a second wall surface which faces the first wall surface across a flow path of the working fluid. A blade height of the variable nozzles at an outlet side is greater than a blade height of the turbine blades at an inlet side.