There are provided a powder supply element adapted to supply powders containing at least toner; developing element adapted to develop an electrostatic latent image by agitating and conveying a developer containing the powders that are supplied by the powder supply element; a toner amount detecting element that is placed in the middle of a conveyance path to connect the powder supply element with the developing element and detects a toner amount per unit volume to be supplied to the developing element; and control element that controls a correction amount with respect to a reference supply amount due to the powder supply element on the basis of a toner amount per unit volume that is detected by the toner amount detecting element.