An image forming apparatus includes an apparatus body, a sheet stacking portion on which a sheet discharged from the apparatus body is to be stacked, an extension member, and an upper device. The extension member is rotatable about a rotating fulcrum between a first position at which the extension member is stored in the sheet stacking portion and a second position at which the extension member extends to downstream of the sheet stacking portion in a sheet discharge direction in which the sheet is discharged from the apparatus body. The upper device is disposed above the rotating fulcrum of the extension member and is supported to be openable by the apparatus body. The upper device in a closed state regulates a rotation of the extension member from the first position toward the second position.