When shortage of a toner residual quantity is detected during printing, toner redetection is performed immediately after completion of printing. This toner redetection is carried out by stopping supply of a high-voltage power to, e.g., a transfer charger and supply of a power to a motor such as a paper carriage motor in order to avoid generation of noise. As a result, a toner sensor can correctly detect the toner residual quantity, and the toner can be appropriately supplied.