A vehicular power source control apparatus includes: two detection devices selected from a door open and close detection device, a seating detection device, a belt detection device, a gripping detection device, a brake detection device, or a shift lever position detection device; and a power source control device to turn on the power source when a power source turn-on condition provided by two predetermined detection results is established. The two predetermined detection results are selected from detection results that the door is closed, the driver sits down on the driver seat, the driver fastens the seat belt, the driver grips the steering wheel, the driver puts on the brake pedal, or the shift lever position of the vehicle is a parking position or a neutral position.