PURPOSE: To enable the positive skew correction and high speed conveyance of sheets by providing a sheet contact piece and a locking piece respectively of specified dimension protrusively at a hollow tube body fitted with play to the drive roller shaft of a pair of inserter rollers, and making the contact piece face selectively upstream in the sheet conveying direction from the nip part of the inserter roller pair at the sheet skew correcting time and retreat at the sheet conveying

CONSTITUTION: A hollow tube body 24 is fitted with play to a drive roller shaft 22 so as to constrain the axial movement. The outer periphery of the hollow tube body 24 is protrusively provided with a sheet contact piece 25 and a locking piece 26 integrally in the position relation of 180°. The contact piece 25 is set to larger radial dimension than the radius of a drive roller 21, and the locking piece 26 is set to smaller radial dimension than the radius of the drive roller 21. When a stopper 28 is engaged with the locking piece 26 by the action of a solenoid 29, the contact piece 25 is positioned upstream in the sheet conveying direction from the nip part of the drive roller 21 and a driven roller 23. The tip of a conveyed sheet thereby comes in contact with the contact piece 25, and its skew state is corrected. The sheet is conveyed by the release of lock between the stopper 28 and the locking piece 26.