A feeding device of a paintball marker gun includes a signal transmitter, a signal receiver, and a paintball feeding unit containing paintballs; the signal transmitter is electrically connected to a controller held in the pistol grip; the paintball feeding unit is connected to the signal receiver, and it includes a stepping motor; when the trigger of the paintball marker gun is pressed to shoot a paintball, the signal transmitter will transmit a signal immediately, which will be received through the signal receiver such that the stepping motor of the paintball feeding unit will start rotating so as to feed a paintball to a main body of the paintball marker gun, thus making shooting and feeding of paintballs happen in a synchronized manner as well as preventing blockage and jams of paintballs.