To easily perform installation to an industrial machine, to recognize and prove precise operation time by installing a time measurement unit, recording the time of engine start and engine stoppage, performing transfer to a dedicated base stand which is the port of a separately installed computer and summing up and displaying operation data.

When a customer starts the engine of a building machine, the current of 24V is made to flow from a battery and is made to flow from a case into a measurement unit 2. For the start time when the engine is started, a ROM stores clock signals. The partway passing time is not stored. When the engine is turned OFF, the ROM stores the clock signals for the end time. When the customer ends the use of the building machine and returns the building machine, a use trader meets him/her at the job site or the like, and at the time, measurement data are pulled out from the measurement unit 2 set at a hidden position, transferred to the dedicated base stand 10 of an office or the like and stored in the computer 30. Thus, the operation time of the building machine is precisely recorded.