A cryocooler includes a compressor, an expander, a gas line that allows a working gas to be circulated between the compressor and the expander and includes a high pressure line through which the working gas is supplied from the compressor to the expander and a low pressure line through which the working gas is collected from the expander to the compressor, a bypass line that connects the high pressure line to the low pressure line such that the working gas bypasses the expander and returns from the high pressure line to the low pressure line, and a bypass flow rate control unit that controls a flow rate of the working gas flowing in the bypass line to provide pressure control of the gas line. The bypass line includes a variable flow rate bypass and a fixed flow rate bypass.