PURPOSE: To facilitate the dust waterproof measures at a lead wire attachment portion by covering the part of an appliance body where an annularly raised portion or an annular groove and a lead wire connection terminal side are formed and a side end portion of the appliance body with a covering member of a plastic material.

CONSTITUTION: Of the peripheral side of a switch body 30, a smaller diameter portion provided with annularly raised parts 33, 34, a terminal base 36 closing one of openings of the switch body 30, and the circumference of ends of lead wires covered with a covering member 58 are formed with thermoplastic resin. Circular grooves 59, 60 are formed around the lead wires 47, 48 of the covering member 58. After fixing the lead wires 47, 48 directly to plates 43, 44 and installing various members to the switch body 30, the periphery of the switch body 30 is covered with the covering member 58. Dust and water prevention effects are obtained around the portion where the lead wires 47, 48 are attached by expansion and contraction of the covering member 58.