A spray gun adjusting device for adjusting painting position of spray gun includes a first axis mechanism and a second axis mechanism slidably positioned on first axis mechanism. First axis mechanism includes a screw rod extending along first direction, a first sliding block, a screw nut sleeved on the screw rod, a first bevel gear fixed to screw nut, a second bevel gear meshing with first bevel gear, and a first driving shaft fixedly connected to second bevel gear, and the screw nut and first driving shaft are rotatably positioned on first sliding block. Second axis mechanism includes a sliding rod along second direction, a second sliding block slidably sleeved on sliding rod, a gear rack fixed to sliding rod, a gear meshing with gear rack, and a second driving shaft fixed to the gear, and second sliding block is fixed to first sliding block of first axis mechanism.