PURPOSE: To make it possible to be excellent in the detecting sensitivity of a reed switch and also it possible to have the appropriate working temperature characteristic thereof, by forming a movement regulating portion which regulates the movement of a thermally sensitive magnetic body and each permanent magnet, both on the reed switch in the longitudinal direction thereof, upon a heat conductivity retaining member.

CONSTITUTION: A thermally sensitive magnetic body 12 and permanent magnets 13, 14 are respectively engaged between riser segments 17e, 17f almost simultaneously with locating a reed switch 11, whereby the movement of the thermally sensitive magnetic body 12 and each of the permanent magnets 11, 14 in the longitudinal direction of the reed switch 11 is regulated. Namely, the thermally sensitive magnetic body 12 and the permanent magnets 13, 14 are respectively located and temporarily fixed onto respective appropriate positions by the riser segments 17e, 17f even without using an adhesive agent. The omission of this adhesive agent from its use makes it possible to manufacture a reed switch having its appropriate working temperature characteristic.