An image forming apparatus includes a sheet separation device, a first sheet feeder, a second sheet feeder, an image forming device, a heat source, and a circuitry. The sheet separation device is configured to separate a two-ply sheet in which two sheets are overlapped and bonded together at one end as a bonding portion of the two-ply sheet. The first sheet feeder is configured to feed the two-ply sheet. The second sheet feeder is configured to feed an inner sheet to be inserted between the two sheets. The image forming device is configured to form an image on the inner sheet fed from the second sheet feeder. The heat source is disposed upstream from the sheet separation device in the sheet conveyance direction. The circuitry is configured to cause the two-ply sheet fed from the first sheet feeder, to detour the heat source to the sheet separation device.