Abstract: An electronic apparatus for measuring cumulative power-on time of an electronic device is provided with: a capability of measuring the power-on time of the device; a nonvolatile memory having at least three memory areas, each of these areas used to cumulatively store the measured power-on time; and a capability for accurately measuring the cumulative power-on time by comparing the data stored in the memory areas and selecting the information that is most closely repeated in the majority of those memory areas. Also, a method of measuring cumulative power-on time of an electronic device is provided which consists of the steps of: measuring the power-on time of the device; writing the measured power-on time in at least three areas of a nonvolatile memory; and accurately measuring the cumulative power-on time by comparing the data stored in the memory areas and selecting the information that is most closely repeated in the majority of those memory areas.