An auxiliary heating apparatus for a vehicle may include a PTC (“Positive Temperature Coefficient”) heating module including a PTC element, and positive and negative terminal boards supplying power to the PTC element, the PTC heating module being disposed between coolant tubes of a heater core of an air conditioning system for the vehicle, a radiation fin provided on each of opposite sides of the PTC heating module to promote a radiation of heat of the PTC heating module, and a holding unit securing the PTC heating module to the coolant tubes.