An image forming apparatus includes a developer container having a movable wall therein, a determination unit, a movable wall driving unit, and a movable wall driving controller. The determination unit outputs first determination information when a number of outputs of a signal indicating that a detection sensor has detected a developer is less than a threshold value, and outputs second determination information when the number of outputs thereof is equal to or greater than the threshold value. The movable wall driving unit includes a first driving motor for moving the movable wall and a first driving circuit for controlling driving thereof. The movable wall driving controller includes a signal controller. The signal controller transmits a drive permission signal for the first driving motor when the first determination information is output, and transmits a drive non-permission signal for the first driving motor when the second determination information is output.