Through stroke control whereby the stroke of a piston is detected and controlled to be equal to a target stroke, the piston is prevented from colliding with a displacer, and the refrigerating performance of a Stirling refrigerator is enhanced. Different target strokes corresponding to different operation conditions of the Stirling refrigerator are stored in a storage portion in a control box, so that a linear motor can be driven with a target stroke that suits the current operation condition. Thus, the piston is prevented from colliding with a displacer, and the refrigerating performance of a Stirling refrigerator is further enhanced.