An image forming apparatus includes a toner bottle, a supply unit that supplies toner from the toner bottle to a downstream side, a door that is openably provided to execute toner replenishment, an opening/closing sensor that senses opening/closing of the door, and a unit that renders the supply unit inoperable if the door is open. If the opening/closing sensor detects the opening of the door, counting of the number of prints is started. Then, the control unit detects whether the door is closed. If the door is still opening, the control unit checks whether the number of prints has reached a predetermined value. If not, the control unit sets the image forming apparatus in a printing state. If yes, the control unit stops the printing operation. If the closing of the door is detected, the control unit resets the count value. Subsequently, the control unit determines whether the initial value of the number of prints, which is set through a control panel at the time of starting the printing operation, is reached. If the initial value is reached, the printing operation is completed.