PURPOSE: To realize seal structure sufficiently enough to avoid switch function loss by putting a seal cover on a switch body after solidification of the first injected liquid filler, and heaping up the liquid filler around this for sealing.

CONSTITUTION: A seal plate 24 is provided inside a slide plate 23, and adhesive 27 is applied around this for sealing. In a horizontal condition, liquid silicon rubber is injected as much as its liquid surface becomes consistent with the top surface of a circuit board 4, and after its solidification a seal cover 26 is put on a switch body 3. Next, the liquid silicon rubber is heaped up around the seal cover 26 so as to seal the junction parts of the seal cover 26 and the circuit board 4 as well as a seal plate 24. After its solidification, front and back panels 2, 3 are united and the liquid silicon rubber 16 is filled in the gap between both. In this way, the seal cover 26 covers movable parts of a switch body 13 and a slider 20. Thereby, sealing can be securely performed without giving any obstruction to the operation of a slide switch.