Markers having a shape defining an edge portion of a radiation image area are recorded together with radiation images in stimulable phosphor sheets in a position fixed with respect to the radiation images. The stimulable phosphor sheets are scanned with stimulating rays, and the edge portion defined by the markers is photoelectrically detected. Read-out of the image signals of the radiation images is conducted by using the detected signal of the edge portion as the read-out synchronizing signal, thereby to obtain the image signals corrected for deviations in position among the radiation images.