Stimulable phosphor sheets are circulated through an image recording section for recording radiation images on the stimulable phosphor sheets, an image read-out section for scanning the stimulable phosphor sheets by stimulating rays and detecting light emitted thereby upon stimulation, and an erasing section for releasing radiation energy remaining in the stimulable phosphor sheets. Time elapsed after the radiation energy remaining in each stimulable phosphor sheet was released is measured, and image recording on each stimulable phosphor sheet is detected. A time measurement signal and an image recording detection signal are sent to a control device which activates a sheet circulating and conveying system to send the stimulable phosphor sheet to the erasing section when the time elapsed after releasing of the radiation energy remaining in the stimulable phosphor sheet reaches a predetermined length prior to image recording on the stimulable phosphor sheet.