PURPOSE: To eliminate the necessity of a measurement program and to prevent the deterioration of the processing capacity of a processor owing to the measurement program by installing a time measurement means, a measurement period pulse generation means and a measured result holding means.

CONSTITUTION: The time measurement means 2 inputs active display information from the processor 6 and a clock pulse, counts the clock pulse so as to output a time measurement value while active display information is inputted. The measurement period pulse generation means 3 inputs and counts the clock pulse and outputs the measurement period pulse whenever the number of previously set times is counted. The measurement result holding means 4 inputs the time measurement value from the time measurement means 2, and the measurement period pulse from the measurement period pulse generation means 3, holds the inputted time measurement value and outputs it to a measured result display means 7 whenever the measurement period pulse is inputted. Thus, the using rate of the processor is measured without using the measurement program which brings the deterioration of the processing capacity of the processor.