A spray gun includes a spray gun main body and an adjustment valve. The spray gun main body has an air intake passage, a first air outlet passage, a second air outlet passage, and a mounting hole defined therein. The mounting hole is in communication with the air intake passage, the first air outlet passage and the second air outlet passage. The adjustment valve is mounted to the spray gun main body and located in the mounting hole. The adjustment valve includes a first operating member and a second operating member. The second operating member is movably mounted on the first operating member.