Image forming apparatus and winding-deviation prevention method

In a front/back reversing unit, a base metal sheet having rollers attached thereon is engaged with a rotation spindle fixed to a fitting such that the base metal sheet is rotatable in a horizontal direction. When an operation of rolling up a print target medium is started and if winding tension with respect to the print target medium to be wrapped around a winding shaft becomes unbalanced, the front/back reversing unit rotates in accordance with the winding tension so as to balance the winding tension. Then, when the winding tension applied to the print target medium becomes balanced, the front/back reversing unit is returned to its original position by an elastic member, and the roller of the front/back reversing unit and the winding shaft become substantially parallel to each other.