To reduce the number of part items so as to attain miniaturization by fixing a temperature control element between a pair of flanges of piping, and driving a valve member by the displacement of a diaphragm caused by expansion/contraction of an expansion medium to communicate or cut off a lead-in passage and a lead-out passage.

Flat end faces 22, 23 corresponding to flanges 5, 6 and a lead-in passage 26 or a lead-out passage 18 are formed at a member constituting a temperature control element 2. When the temperature on the piping 3 side is lowered, an expansion medium 20 is contracted to displace a diaphragm 15 upward, and a valve member 17 is separated from a lower wall member 19 to open the lead-out passage 18 and to communicate the lead-in passage 26 and the lead-out passage 18 with each other. When the temperature on the piping 3 side rises due to the discharge of condensed water, the expansion medium 20 is expanded to displace the diaphragm 15 downward, and the valve member 17 is seated on the lower wall member 19 to close the lead-out passage 18 and to cut off communication between the lead-in passage 26 and lead-out passage 18. The number of part items is thereby reduced to attain miniaturization.