To improve skew correction efficiency, by effectively using moving operation of register roller pairs for moving a sheet in the width direction.

This image forming device 60 includes a register device 65 having this side-innermost side movable units 82A and 82B respectively arranged on both sides of a carrying passage 84 and correcting a skew of the sheet by registering the side end of the sheet and the register roller pairs 7 for making the center of the sheet coincide with the center CT of the carrying passage by moving the sheet of registering the side end by this side-innermost side movable units in the width direction of the carrying passage 84. Since register roller pairs 7 stop by holding and moving the sheet of correcting the skew by one movable unit among this side-innermost side movable units to the center CT of the carrying passage and moves the sheet to the center of the carrying passage by holding the sheet continuously carried by correcting the skew by the other movable unit from its stopped state, reciprocating operation in the sheet width direction is effectively used.