In an image forming apparatus, a sheet reversing mechanism is configured to take over and transfer, at a transfer speed Vr, a print sheet with an image already formed on one side being transferred at the transfer speed Vr from a first transfer mechanism, to stop the print sheet once, then to start transfer of the print sheet in an opposite direction, and to pass the print sheet to a second transfer mechanism at the transfer speed Vr. The first and second transfer mechanisms are located on upstream and downstream of a switchback reverse path for reversing print sheets respectively Upon lapse of a time T1 after detection of the print sheet by a print sheet detection unit, a transfer control unit drives the sheet reversing mechanism to start acceleration from a stopped state to the transfer speed Vr, the time T1 calculated based on the transfer speed Vr.