To provide a slide bearing support structure for an idler gear, capable of improving robustness to low cost and temperature variation.

The slide bearing support structure is characterized in that: a support structure with a lower-cost slide bearing 3 is employed; the same material is used for the idler gear 1 and the slide bearing so that an equal clearance can be made, under a normal or high temperature, between a shaft 1a of the idler gear 1 and holes 5 on a rear side plate 4 of a body of an image forming apparatus and in a driving bracket 6 for supporting the idler gear; and then the holes 5 are thermally expanded in an elliptical shape having a shorter axis in the direction of the application of a radial load.