Disclosed a trigger switch including: a case having a switch chamber in which a switch mechanism is arranged in a sealed state; a plunger inserted slidably into a shaft hole formed on one end side of the case, coupled to the switch mechanism, and biased forward; and a trigger provided on a distal end of the plunger for operating the switch, wherein the switch mechanism includes an air pressure stabilizing mechanism configured to cancel an air compressing action in the interior of the switch chamber caused by the switch mechanism moving in the interior of the switch chamber. The air pressure stabilizing mechanism includes a communication hole extending from a rear end opening facing the switch chamber to a distal end opening on the plunger, and a plunger-engaging portion of the trigger includes a discharge port communicating with the communication hole and configured to release air from the communicating hole.