FUEL CELL FLUID MACHINE

A fuel cell fluid machine includes a rotary shaft, an electric motor, a compression unit, and a rotation assist unit. The rotation assist unit includes a turbine wheel and a turbine housing. Exhaust gas discharged from a fuel cell stack is introduced to the turbine chamber. The exhaust gas then flows in the radial direction of the rotary shaft and is discharged in the axial direction of the rotary shaft. This rotates the turbine wheel. A diameter of the turbine wheel and a diameter of the shroud surface gradually increase from an upstream side to a downstream side in a flowing direction of the exhaust gas.