To surely and easily flocculate an excessive wax component contained in car-washing drain together with stain substances with a flocculating agent to ensure the improvement in the quality of the car-washed drain.

This car-washing detergent used before coating a car with an aqueous wax prepared by dispersing a wax component in water with a surfactant is characterized by adding the flocculating agent to the surfactant having washing power for a car body and a brush.