A cryocooler includes: a magnetic shield axially extending along a second-stage cylinder from a second-stage cooling stage outside the second-stage cylinder and disposed separated from a first-stage cooling stage by an axial separation distance, wherein an annular space open to a helium atmosphere is formed between the second-stage cylinder and the magnetic shield, and the axial depth of the annular space is longer than the axial separation distance; and a convection suppression member, for suppressing axial convection of helium gas in the annular space caused by temperature difference between the second-stage cylinder and the magnetic shield, is disposed in the annular space and is of longer axial length than the axial separation distance.