PURPOSE: To make it possible to monitor execution instructions in real time without the influence upon a measured object program, by constituting the execution instruction monitor unit with hardware.

CONSTITUTION: An arbitrary instruction is set to the instruction set part by the manual set mechanism. Instruction detecting part 23 compares the fetched instruction with the instruction held in the instruction set part; and if they coincide with each other, a signal is issued. The first and the second counting parts 27 and 28 count an instruction fetch frequency of processor 10 and the number of instructions which coincide with the instruction set in instruction set part 22. Rate operating part 29 operates the product between count values of the first and the second counting parts 27 and 28. The value of rate operating part 29 and values of counting parts 27 and 28 are supplied to bus 1 and are printed finally as the constitution ratio and the use frequency of instructions used in the measured program.