A loosening fan provided in an air blowing unit blows at sheets stacked on a tray to loosen the sheets. The following expressions are satisfied:0. The interlocking chain type forward and backward actuating device includes chain-guide grooves formed so as to equalize an interlocked-state pin-to-pin distance between a pair of connecting pins that face each other in a chain interlocking imaginary plane and a rigid-state pin-to-pin distance between a pair of connecting pins. An aligning phase initially is energized to orient the rotor so as to provide adequate starting phase start-up torque.