Method for counting event and image formation device implementing the method

[Subject] Though it is possible to reduce the cost for nonvolatile memory equipment, a dogged method is offered to various kinds of faults. [Solution means] In the equipment 101 which has operational mode and non-operational mode, It is a method for counting an event by the volatile counter 109 and the fixity electronic memory 111 including N memory areas, a) When the step and b counted value which count an event with the volatile counter 109 increase only severalM predetermined, Or when the equipment 101 shifts to non-operational mode, the preservation to one of the memory areas of counted value, The method containing the step which initializes the counter 109 at the maximum of the counted value saved in N memory areas when the step which changes cyclically the memory area where counted value is written in, and performs it, and the c equipment 101 shift to operational mode. [Selection figure] Fig. 1