To determine whether a power supply has abnormality, when power supply voltage drops and to display a warning when the power supply has abnormality.

An image forming apparatus is provided with: a power supply voltage measuring means which measures the voltage of the power supply input to the image forming apparatus; an individual unit power supply voltage drop amount measuring means which measures a power supply voltage drop amount when a plurality of units are energized independently by the power supply voltage measuring means; a table which stores the individual voltage drop amount of the plurality of units measured by the individual unit power supply voltage drop amount measuring means; a display means which displays information on the image forming apparatus; and a control means which controls the image forming apparatus. The control means determines the threshold of the power supply voltage drop amount, on the basis of the total value of the voltage drop amount corresponding to the unit while being energized of the individual voltage drop amounts of the plurality of units stored in the table and discriminates that the power supply has abnormality and performs the warning display by the display means, when the voltage drop amount of the power supply measured by the power supply voltage measuring device is larger than the threshold.