PURPOSE: To enable optimum design of a program and an optimum design of task by providing a mechanism that measures a processing time occupied by each part of program to be developed in an executing state in a program developing device.

CONSTITUTION: A program developing device writes 1 in an FF 23 connected to a bus 15 (program developing device host processor bus). An AND circuit is opened, and a unit time clock signal 25 is impressed to the count up terminal of a counter 22. The counter 22 performs a count up operation from a preset value by an RAM3. This count up operation is continued until next address information timing signal 16 is sent out from a debugged microprocessor 1. When a signal 16 is sent out, the value of the counter 22 is written in the same storing position of the RAM3. After writing, the same operation is repeated by the renewed address. Accordingly, the total of time in access with the address A is stored in the memory position corresponding to the address A of the RAM3.