To reduce biting of foreign matters in a fluid between a first and second spring bearings and a coil spring.

A float 3, change-over valve 4, and snap mechanism 5 are built into a sealed vessel 2. The snap mechanism 5 has: a swing shaft 35 supported in the sealed vessel 2; a float arm 34 and auxiliary arm 37 rotating around the swing shaft 35; a first shaft 39 supported by the float arm 34; a second shaft 41 supported by the auxiliary arm 37; the first spring bearing 40 rotating around the first shaft 39; the second spring bearing 42 rotating around the second shaft 41; and the coil spring 38 installed between the first and second spring bearings 40 and 42. The coil spring 38 is installed in a tube portion 48 continuing between the first and second spring bearings 40 and 42. One end of the coil spring 38 is coupled to the spring bearing sliding into the tube portion 48. The tube portion 48 is provided independently of the first and second spring bearings 40 and 42.