A radiation image signal output control method in which distance information that indicates a distance between a radiation image detection cassette and a receiving unit is obtained by a distance information obtaining means, and wireless signals are controlled by an output control means to be outputted from the radiation image detection cassette if the distance indicated by the distance information obtained by the distance information obtaining means is less than or equal to a predetermined value, and not to be outputted therefrom if the distance is greater than the predetermined value.