To easily and highly precisely set the operation temperature of a thermostat.

The cam face 63a of a cam body 60 turned by a dial 40 through an adjusting axis 30 is made to face an engaged pin 27 moving with the expansion/contraction of the rod of a thermostat 20. When the rod expands, the cam body 60 is pushed by the engaged pin 27 and it moves along the adjusting axis 30 and advances an operation bar 50. An adjusting margin L being an interval between the cam face 63a and the engaged pin 27 is adjusted by turning the cam body 60 by the dial 40 and a setting temperature is changed. The operation valid angle of the cam face 63a is set to be within one turn to about 200° and the whole area of an operation temperature is covered within one turn of the dial 40.