In a cryogenic refrigerator using a Gifford MacMahon (GM) cycle, a rotary valve device (RV) for controlling the supply and discharge of refrigerant gas with respect to the refrigerator (2) is adapted by a reversible motor (15) to be rotated in normal and reverse directions, and during the rotation in the normal direction, a cooling mode operation for producing cold by an adiabatic expansion is effected, and during the rotation in the reverse direction, a temperature-raising mode operation for producing heat by an adiabatic compression is effected. In order that the optimum efficiency can be obtained in each of the cooling mode operation and the temperature-raising mode operation, the timing of opening and closing of the rotary valve device (RV) with respect to the reciprocal movement of displacers (3a, 3b) during the rotation in the normal direction is made different from said timing during the rotation in the reverse direction. As a result, the time required for raising the temperature of a cooling portion in a cryogenic condition to the normal temperature can be shortened without the need for any special equipment.