A developer container is provided with a container body. An opening is formed through the container body. An opening/closing lid closes the opening. A lid holding frame holds the opening/closing lid in such a manner that the opening/closing lid can move between an open position and a closed position. A stopper stops the opening/closing lid and thereby preventing it from moving toward the open position in a state that the opening/closing lid is located at the closed position. A contact portion comes into contact with a hook portion provided in a container receiving portion when the developer container is inserted into the container receiving portion. A deformable portion deforms the stopper to such an extent that the stopping of the opening/closing lid by the stopper is canceled when the developer container is inserted into the container receiving portion and the contact portion comes into contact with the hook portion.