A paper feeding device includes a pickup roller mechanism disposed at an entrance of a paper feeding path, and a separation mechanism disposed to a rear end of the pickup roller mechanism. The pickup roller mechanism includes a first pickup unit positioned at the entrance of the paper feeding path, a second pickup unit mounted to a rear end of the first pickup unit, and a third pickup unit disposed to a rear end of the second pickup unit. The second pickup unit includes a first driving gear. The third pickup unit includes a second driving gear, and a transmission belt looped around an outer periphery of the first driving gear and an outer periphery of the second driving gear.