PURPOSE: To form a device small in size and to solve the problem of pricing for use for most equipment or the like by separating the device to a detecting part and a display part, and mounting only the detecting part on the equipment.

CONSTITUTION: When the equipment 1 is operated, an electrical signal is inputted to an operation detection circuit 4, and it is processed at a clock circuit 5, and is stored in an operating time memory circuit 6, and since the power source 1a of the equipment is disconnected when the operation of the equipment is stopped, a power source switching circuit 3 is operated so as not to dissipate data. When working time is detected, a reader is connected to an external output circuit part, and the working time is displayed on the display part provided at the reader. In such a way, an inexpensive and accurate detecting method for the working time of the equipment can be obtained.