To simply transmit operating data to a center side computer through prescribed operation by a user of installed machines at a required time without the need for automatic transmission of the operating data of the installed machines from a factory side computer to the outside of the factory through a communication channel.

A slave computer employing a pre-installed 1st operating data collection program periodically collects and stores the operating data from the installed machines (S1). The center side host computer transmits 2nd operating data collection program attached to electronic mail to a factory side master computer (S2). The master computer executes the program under a prescribed operation (S3). The master computer collects the operating data stored in the slave computer by using the 2nd operating data collection program and a storage device of the master computer stores operating data files (S4).