Method of controlling power output of a stirling engine

A method of controlling power output of a Stirling engine having a casing, a displacer slidably fitted in the casing, and a working piston disposed under the displacer and slidably fitted in the casing, comprising the steps of: providing the casing with a bleeding passage extending radially outwardly between the displacer and the working piston, and providing means for adjusting volume of the bleeding passage, whereby the power output of the Stirling engine can be accurately controlled.