A trigger switch, comprising: a switching operation unit configured to control the rotation of a motor between a normal rotation and a reverse rotation; a sliding operation unit configured to be coupled to a trigger lever; a case configured to store the switching operation unit and the sliding operation unit; a cover configured to close an opening surface of the case, the switching operation unit being partly built into an upper position of the case, and including a switching contact strip formed of a conductive metallic member which generates switching signals on a side surface of a rear end portion thereof, and a switching lever having a revolving shaft rotatably provided at a substantially center position, the sliding operation unit being partly built into a lower position of the case, and including a speed control unit having sliding elements (42, 43) which is configured to move in association with the operation of the trigger lever, and a sliding shaft coupled at a rear end to the speed control unit and allows the trigger lever to be mounted on a distal end portion thereof, the cover including a sliding circuit board having contact elements (45, 46, 47, 48) on which the sliding elements (42, 43) slide, wherein the case is formed with a speed control unit storage chamber configured to store the speed control unit, a revolving shaft storage chamber configured to store the revolving shaft of the switching lever, and a contact strip member storage chamber provided with continuing from the revolving shaft storage chamber through a shielding member therebetween and configured to store the contact strip member of the switching lever, the revolving shaft storage chamber is formed with a revolving shaft engaging hole configured to allow the revolving shaft to be inserted in an engaged state on an upper portion thereof on the side of the trigger lever, characterised by a waterproof packing formed of rubber and configured to include a rectangular engaging portion configured to allow penetration of an arm member of the switching lever exposed outside therethrough and to cover the arm member, and a chamber waterproof member opening on the lower side and having a size to cover a top surface of the revolving shaft storage chamber so that the waterproof packing fittedly covers at least a portion including a periphery of a portion in the proximity of the revolving shaft of the arm member which forms a distal end side of the switching lever and a top surface of the revolving shaft storage chamber, whereby the waterproof packing covers at least a gap between the switching lever and the revolving shaft engaging hole and is provided to prevent entry of water therein. a switching operation unit configured to control the rotation of a motor between a normal rotation and a reverse rotation; a sliding operation unit configured to be coupled to a trigger lever; a case configured to store the switching operation unit and the sliding operation unit; a cover configured to close an opening surface of the case, the switching operation unit being partly built into an upper position of the case, and including a switching contact strip formed of a conductive metallic member which generates switching signals on a side surface of a rear end portion thereof, and a switching lever having a revolving shaft rotatably provided at a substantially center position, the sliding operation unit being partly built into a lower position of the case, and including a speed control unit having sliding elements (42, 43) which is configured to move in association with the operation of the trigger lever, and a sliding shaft coupled at a rear end to the speed control unit and allows the trigger lever to be mounted on a distal end portion thereof, the cover including a sliding circuit board having contact elements (45, 46, 47, 48) on which the sliding elements (42, 43) slide, wherein the case is formed with a speed control unit storage chamber configured to store the speed control unit, a revolving shaft storage chamber configured to store the revolving shaft of the switching lever, and a contact strip member storage chamber provided with continuing from the revolving shaft storage chamber through a shielding member therebetween and configured to store the contact strip member of the switching lever, the revolving shaft storage chamber is formed with a revolving shaft engaging hole configured to allow the revolving shaft to be inserted in an engaged state on an upper portion thereof on the side of the trigger lever, characterised by a waterproof packing formed of rubber and configured to include a rectangular engaging portion configured to allow penetration of an arm member of the switching lever exposed outside therethrough and to cover the arm member, and a chamber waterproof member opening on the lower side and having a size to cover a top surface of the revolving shaft storage chamber so that the waterproof packing fittedly covers at least a portion including a periphery of a portion in the proximity of the revolving shaft of the arm member which forms a distal end side of the switching lever and a top surface of the revolving shaft storage chamber, whereby the waterproof packing covers at least a gap between the switching lever and the revolving shaft engaging hole and is provided to prevent entry of water therein.