A nozzle insertion member that is arranged in a powder container (32; 1032) used in an image forming apparatus and that includes a nozzle insertion opening (331; 1331) into which a conveying nozzle for conveying powder supplied from the powder container (32, 1032) is inserted, the nozzle insertion member (330; 1330) comprising: an opening/closing member (332; 1332) to move to an opening position so as to open the nozzle insertion opening (331; 1331) by being pressed by the conveying nozzle thus inserted, and to a closing position so as to close the nozzle insertion opening (331; 1331) when the conveying nozzle is separated from the nozzle insertion member (330; 1330); a supporting member to support the opening/closing member (332; 1332) so as to guide the opening/closing member (332; 1332) to the opening position and the closing position, the supporting member being formed with an opening thereon; and a biasing member (336; 1336) that is provided to the supporting member and that biases the opening/closing member (332; 1332) toward the closing position, wherein when the powder in the powder container (32; 1032) is supplied to the conveying nozzle inserted into the nozzle insertion opening (331; 1331) along with rotation of a rotary conveyor arranged inside the powder container (32; 1032), the supporting member rotates with the rotation of the rotary conveyor, the opening/closing member (332; 1332) is rotated by a drive transmitting mechanism (332g, 335d) along with rotation of the supporting member, the drive transmitting mechanism (332g, 335d) includes an elongated member that is arranged on the opening/closing member (332; 1332) so as to extend in a longitudinal direction of the conveying nozzle and that penetrates through the opening formed on the supporting member; a drive transmitted portion formed on the elongated member; and a drive transmitting portion that is formed on an inner surface of the opening characterized in that the drive transmitted portion is a flat guiding portion and configured to pass through the drive transmitting portion whereby the drive transmitting portion and the drive transmitted portion face each other and come in contact with each other. an opening/closing member (332; 1332) to move to an opening position so as to open the nozzle insertion opening (331; 1331) by being pressed by the conveying nozzle thus inserted, and to a closing position so as to close the nozzle insertion opening (331; 1331) when the conveying nozzle is separated from the nozzle insertion member (330; 1330); a supporting member to support the opening/closing member (332; 1332) so as to guide the opening/closing member (332; 1332) to the opening position and the closing position, the supporting member being formed with an opening thereon; and a biasing member (336; 1336) that is provided to the supporting member and that biases the opening/closing member (332; 1332) toward the closing position, wherein when the powder in the powder container (32; 1032) is supplied to the conveying nozzle inserted into the nozzle insertion opening (331; 1331) along with rotation of a rotary conveyor arranged inside the powder container (32; 1032), the supporting member rotates with the rotation of the rotary conveyor, the opening/closing member (332; 1332) is rotated by a drive transmitting mechanism (332g, 335d) along with rotation of the supporting member, the drive transmitting mechanism (332g, 335d) includes an elongated member that is arranged on the opening/closing member (332; 1332) so as to extend in a longitudinal direction of the conveying nozzle and that penetrates through the opening formed on the supporting member; a drive transmitted portion formed on the elongated member; and a drive transmitting portion that is formed on an inner surface of the opening characterized in that the drive transmitted portion is a flat guiding portion and configured to pass through the drive transmitting portion whereby the drive transmitting portion and the drive transmitted portion face each other and come in contact with each other. an elongated member that is arranged on the opening/closing member (332; 1332) so as to extend in a longitudinal direction of the conveying nozzle and that penetrates through the opening formed on the supporting member; a drive transmitted portion formed on the elongated member; and a drive transmitting portion that is formed on an inner surface of the opening characterized in that the drive transmitted portion is a flat guiding portion and configured to pass through the drive transmitting portion whereby the drive transmitting portion and the drive transmitted portion face each other and come in contact with each other.