PURPOSE: To rapidly and easily know accurate load history by allowing a slave computer to measure and edit system load based upon an instruction applied from a master computer and transmit a specified information based upon a request applied from the master computer.

CONSTITUTION: A system load measuring instruction program 16 sends a system load measuring request to a transmission line 3 through a transmitter 13. The measuring request is received by a transmitter 23 in the slave computer 2 and sent to a CPU 21 which transmits the request to a load measurement control editing program 25 stored in a main storage device 22. The program 25 requests an operating system 24 to measure system load in accordance with the received measurement request. The OS 24 executes prescribed measurement at each fixed period and stores the measured result in a load measurement history area 26. At the time of receiving an output request from the master computer 1, specified up-to-date system load history data are extracted and sent from the transmitter 23 to the transmission line 3.