To provide a toner-counting technology enabling proper accounting, in response to the toner usage by a user.

A gradation value, indicating gradation data generated on the basis of an image signal input from an outside device, is integrated by a dot counter 210. A toner counter 220 multiplies coefficient K1 with the counted value DC to calculate the toner amount used for forming a toner image to add offset values Coff1 and Coff2 corresponding to the toner amount consumed by the other reason so as to find the consumption TC1 of the toner of the apparatus as a whole. CPU 101 manages the residual amount of the toner on the basis of the value TC1, and makes the amount TC2 of the toner supplied to the user as the toner image from among the whole toner consumption TC1 an accounting target.