An image forming apparatus includes sheet accommodating cassette for accommodating sheets, a device for forming images on the sheets, a first sheet conveying passage for conveying the sheet to the image forming device from the sheet accommodating cassette, a conveyor for accommodating a bundle of sheets having been subjected to an image forming operation by the image forming means at first sides thereof in a form in which leading edges of the sheets are gradually deviated in a sheet advancement direction, and for conveying the bundle as a whole, a feeder, disposed downstream of the conveyor with respect to the sheet advancement direction, for feeding one by one the sheets of the bundle from the sheet closest to the feeder, a second sheet conveying passage merging into the first passage for refeeding to the image forming device the sheets fed by the feeder, and a confining device for confining the sheets of the bundle other than the sheet being fed by the feeder.