An electric caulking gun has a body and an actuating assembly. The body has a pushing shaft, a motor, a gearbox, a transmission device, a circuit board and a switch. The gearbox has a sun gear with multiple mounting slots. The actuating assembly is mounted in the body, is connected to the switch and engages the sun gear and has a connecting arm, a linking arm, an actuating element, an oscillating arm and a pressing button. The connecting arm is pivotally connected to the switch. The linking arm is connected to the connecting arm. The actuating element is mounted in the body, selectively engages one of the mounting slots and has a wedge mount and an engaging block. The oscillating arm is connected to the body and is connected to the connecting arm. The pressing button is movably mounted in the body and is connected to the oscillating arm.