1. A detecting device for detecting a fake test of Blood Alcohol Concentration (BAC) that a person different from driver of a vehicle takes on behalf of the driver using an alcohol measurement device, comprising: a testee image pick-up means for picking up a face image of a testee shot during an alcohol measurement; a driver image pick-up means for picking up a face image of the driver shot within a predetermined period of time before or after the alcohol measurement; and a checking means for checking the testee and the driver based on the face images of the testee and the driver.