A Stirling engine is provided with a piston and a displacer. When the piston is made to reciprocate inside a cylinder by a linear motor, the displacer reciprocates inside a cylinder with a predetermined phase difference relative to the piston. In parts of the displacer and the cylinder that receives the displacer, the parts facing a compression space are made of metal, and the parts facing an expansion space are made of a low-thermal-conductivity material. In the metal part, the fitting accuracy is defined.