A toner container for connection to a toner-container holder of an image forming apparatus, the toner container comprising: a container body (33Y, 33M, 33C, 33K) configured to contain toner and that includes an opening for discharging toner; and a cap (34Y, 34M, 34C, 34K) that is attached to the container body (33Y, 33M, 33C, 33K) and configured to be held in a non-rotating manner with the toner-container holder, the cap (34Y, 34M, 34C, 34K) including: two side portions; a toner outlet, different from the opening of the container body (33Y, 33M, 33C, 33K) configured to receive toner from the opening of the container body (33Y, 33M, 33C, 33K) and configured to discharge the toner for forming images by the image forming apparatus, the toner outlet being perpendicular to a length of the container body (33Y, 33M, 33C, 33K); a nozzle hole, to receive a nozzle of the image forming apparatus which is parallel to the length of the container body (33Y, 33M, 33C, 33K), the nozzle receiving the toner discharged from the toner outlet while the nozzle is in the nozzle hole, characterized in that a sliding portion (34c1, 34c2) for sliding along the toner-container holder in synchronization with an attachment/detachment operation to/from the toner-container holder, the sliding portion (34c1, 34c2), comprising: a first sliding portion (34c1) which is formed on a bottom face of the cap (34Y, 34M, 34C, 34K) and is arranged under the nozzle hole and is a flat portion configured to face an upward sliding face of the toner-container holder; and a second sliding portion (34c2) which is disposed in each of the two side portions of the cap (34Y, 34M, 34C, 34K) and is a flat portion facing corresponding sideward sliding faces of the toner-container holder. a container body (33Y, 33M, 33C, 33K) configured to contain toner and that includes an opening for discharging toner; and a cap (34Y, 34M, 34C, 34K) that is attached to the container body (33Y, 33M, 33C, 33K) and configured to be held in a non-rotating manner with the toner-container holder, the cap (34Y, 34M, 34C, 34K) including: two side portions; a toner outlet, different from the opening of the container body (33Y, 33M, 33C, 33K) configured to receive toner from the opening of the container body (33Y, 33M, 33C, 33K) and configured to discharge the toner for forming images by the image forming apparatus, the toner outlet being perpendicular to a length of the container body (33Y, 33M, 33C, 33K); a nozzle hole, to receive a nozzle of the image forming apparatus which is parallel to the length of the container body (33Y, 33M, 33C, 33K), the nozzle receiving the toner discharged from the toner outlet while the nozzle is in the nozzle hole, characterized in that a sliding portion (34c1, 34c2) for sliding along the toner-container holder in synchronization with an attachment/detachment operation to/from the toner-container holder, the sliding portion (34c1, 34c2), comprising: a first sliding portion (34c1) which is formed on a bottom face of the cap (34Y, 34M, 34C, 34K) and is arranged under the nozzle hole and is a flat portion configured to face an upward sliding face of the toner-container holder; and a second sliding portion (34c2) which is disposed in each of the two side portions of the cap (34Y, 34M, 34C, 34K) and is a flat portion facing corresponding sideward sliding faces of the toner-container holder. two side portions; a toner outlet, different from the opening of the container body (33Y, 33M, 33C, 33K) configured to receive toner from the opening of the container body (33Y, 33M, 33C, 33K) and configured to discharge the toner for forming images by the image forming apparatus, the toner outlet being perpendicular to a length of the container body (33Y, 33M, 33C, 33K); a nozzle hole, to receive a nozzle of the image forming apparatus which is parallel to the length of the container body (33Y, 33M, 33C, 33K), the nozzle receiving the toner discharged from the toner outlet while the nozzle is in the nozzle hole, characterized in that a sliding portion (34c1, 34c2) for sliding along the toner-container holder in synchronization with an attachment/detachment operation to/from the toner-container holder, the sliding portion (34c1, 34c2), comprising: a first sliding portion (34c1) which is formed on a bottom face of the cap (34Y, 34M, 34C, 34K) and is arranged under the nozzle hole and is a flat portion configured to face an upward sliding face of the toner-container holder; and a second sliding portion (34c2) which is disposed in each of the two side portions of the cap (34Y, 34M, 34C, 34K) and is a flat portion facing corresponding sideward sliding faces of the toner-container holder. a first sliding portion (34c1) which is formed on a bottom face of the cap (34Y, 34M, 34C, 34K) and is arranged under the nozzle hole and is a flat portion configured to face an upward sliding face of the toner-container holder; and a second sliding portion (34c2) which is disposed in each of the two side portions of the cap (34Y, 34M, 34C, 34K) and is a flat portion facing corresponding sideward sliding faces of the toner-container holder.