PURPOSE: To prevent the power source from being left forgetfully ON by displaying the state of the power sources of connected peripheral equipments on a display device when the power source is turned OFF.

CONSTITUTION: This device consists of a power source monitoring means 10, a power source state display means 20, the peripheral equipments 30, the display device 40, a peripheral equipment control means 50, an input processing means 60, an input device 70 such as a keyboard, a power source processing means 80, and a controller 90. The power source monitoring means 10 confirms the states of the electric power by peripheral equipments 30 connected to the peripheral equipment control means 50 and reports the confirmed states of the power sources when inquired of by the power source state display means 20. The power source state display means 20 inquires information regarding the power sources of the respective peripheral equipments 30 of the power source monitoring means 10 when there is a power-OFF indication from a power switch or keyboard, and displays whether or not each peripheral equipment 30 is powered ON on the display device 40.