Developing device and image forming apparatus that detect toner density

A developing section comprising:

• N (N is an integer equal to or greater than two) number of containers that each house a developer including a toner;
• N number of conveying members that stir and convey the respective developers inside the N number of containers;
• N number of first sensors located at the N number of containers each to detect a developer remaining amount inside a respective one of the N number of containers;
• stirring portions located at the respective N number of conveying members to stir the developers at detecting regions opposed to detecting surfaces of the N number of first sensors by rotations of the N number of conveying members;
• a switching unit that selects any one of outputs of the N number of first sensors to output;
• and
• a control unit that receives the selected output to detect a respective one of the remaining amounts of the developers inside the N number of containers,
• wherein the N number of conveying members synchronously rotate at preliminarily set phase differences, and
• the switching unit selects the output of the first sensor corresponding to the conveying member at an angle against the detecting surface that has become a preliminarily set angle.