A variable displacement supercharger includes a turbine having: a turbine housing that forms a scroll flow passage disposed around a turbine impeller; a variable nozzle unit that includes a second nozzle ring that faces the scroll flow passage and forms a part of an inner wall of the scroll flow passage; and an annular seal member that seals the gap between the turbine housing and the second nozzle ring. The seal member has a disc spring structure that is inserted into the gap and biases the turbine housing and the second nozzle ring in an axial direction of rotation, and is arranged further inside than the scroll flow passage in the radial direction of the turbine impeller.