To dispense with excess connecting wirings by accurately recognizing an engine starting start-up state based on a power supply voltage, and surely prevent starter burnout.

This device comprises: a voltage detecting means 1 for measuring power supply voltage Vs of the vehicle starter; a past voltage history reserving means 11 for reserving a history of a past voltage; a present voltage history reserving means 12 for reserving a history of a present voltage; a subtraction means 13 for reading out the history of the present voltage and the history of the past voltage to compute a voltage difference ΔV between the present voltage and the past voltage; a comparison means 14 for comparing the voltage difference ΔV and a predetermined voltage Vr; and a starter off means 15 for turning off the vehicle starter when a state indicating that the voltage difference ΔV is less than the predetermined voltage Vr is continued more than a predetermined time.