To provide a thermostat for controlling the inside temperature of a refrigerator or the like, wherein assembly of a case and a body frame can be achieved without causing cracks and chipping or the like of the case.

A cut-out portion 2 is provided at the side face 1a of a body frame 1 and a tongue portion 3 is provided at part of the cut-out portion 2, and a step portion 7 which contacts the cut-out portion 2 is provided at the side face 5a of the case 5. Then, the tongue portion 3 penetrates into the step portion 7 and a square hole 9 having an outer wall part 8 to contain the tongue portion 3 is provided. Accordingly, the case 5 can be easily inserted along the cut-out portion 2 and the step portion 7 from the opening of the body frame 1, After the tongue portion 3 is inserted into the square hole 9, the tongue portion 3 is bent and fixed to the case 5. Thus, the case 5 can be easily and certainly installed on the body frame 1 without causing cracks and chipping or the like to the case 5.