Provided is a steel tube rust removal device with the automatic paint spraying function. When a control cabinet controls the whole device to operate, a second motor drives a steel tube to rotate while driving a rotary clamping base to rotate, rust removal and polishing are carried out on the inner wall and the outer wall of the steel tube at the same time through an inner wire wheel, an inner polishing wheel, an outer wire wheel and an outer polishing wheel, and a rack and a gear of a first motor are in transmission to control a first paint can, the outer wire wheel and the outer polishing wheel to move horizontally to carry out rust removal, polishing and paint spraying on the outer wall of the whole steel tube evenly, wherein the outer wire wheel and the outer polishing wheel are installed on the first paint can. Meanwhile, a screw rod is driven by a guide wheel and a third motor to rightwards rotate and move, and the rotation direction of the screw rod is opposite to the rotation direction of the steel tube. By means of rust removal and polishing carried out through the inner wire wheel and the inner polishing wheel, spraying on the inner wall of the steel tube through an inner spray gun is ensured. By means of the automatic rust removal and spraying device, harm to physical health of staff by rust and dust is avoided. Meanwhile, due to timely spraying, later corrosion and manpower resource waste caused when the machining time of the steel tube is too long can be prevented.