Radiation image read-out apparatus

A radiation image read-out apparatus comprises a single light guide member constituted of a light guiding material. The light guide member comprises two input end faces for collecting light, which is emitted along a scanning line of stimulating rays and from two surfaces of a stimulable phosphor sheet having a radiation image stored thereon, and output end faces for radiating out the light, which has entered into the light guide member from the two input end faces. A single photodetector is located in close contact with the output end faces and photoelectrically detects the light radiated out of the light guide member. The input end faces of the light guide member comprise a first input end face for collecting the light, which is emitted from the front surface of the stimulable phosphor sheet, and a second input end face for collecting the light, which is emitted from the back surface of the stimulable phosphor sheet. The first and second input end faces of the light guide member stand facing the same scanning line.