A heat gun includes a canister, a first outlet pipe, and an assistant member. The canister includes a columnar sidewall bounding a receiving space and an installation board mounted in the receiving space. The assistant member includes a first vent pipe, and a second vent pipe communicating with the first vent pipe and slidably mounted to the first vent pipe. Top ends of the first outlet pipe and the first vent pipe extend through the installation board and communicate with an upper portion of the receiving space. Bottom ends of the first outlet pipe and the second vent pipe function as outlets of the heat gun.
