PURPOSE: To simplify the construction of a blank retreat preventing means and facilitate the control thereof by forming said means of a pair of retreat preventing rollers.

CONSTITUTION: When a blank P fed by a pair of retreat preventing rollers 8 is detected by a blank sensor 12, drive forces for a pick-up roller 3 and a feed roller 5 are interrupted. Next, a drive force for the retreat preventing rollers 8 is interrupted when the blank P is detected by a blank sensor 13 so that the blank is further fed by the turning force due to the inertia of the retreat preventing roller 8 to abut against the contact portion of a pair of registering rollers 7 being not rotated and stand by under the flexed condition. Then, since the turning force for a reverse roller 6 is interrupted, the contact pressure between the feed roller 5 and the reverse roller 6 derives only from spring pressure. However, since the retreat preventing rollers 8 sandwich the blank P with a predetermined pressure or more, the flexed blank P between said rollers 8 and the registering roller 7 is prevented from retreat.