Abstract: An adjustable jet gun for cleaning machine includes a barrel, a pressure adjustment sleeve fastened to the front end of the barrel and operable to adjust the pressure of water delivered through the adjustable jet gun, a support ring sleeved onto the front end of the pressure adjustment sleeve and holding a steel ball in each of a number of ball racks around the periphery thereof, a sliding sleeve sleeved onto the support ring and movable to force the steel balls out of the inside wall of the support ring, a nozzle head detachably connected to the front end of the support ring and having a positioning groove extending around the periphery of a rear positioning ring thereof for receiving the steel balls to lock the nozzle head to the support ring.