Disclosed herein is a method of obtaining an image signal, comprising the steps of preparing an image recording sheet having a stimulable phosphor layer which emits photostimulated luminescent light in a quantity corresponding to stored energy when irradiated with stimulating light, scanning the image recording sheet in horizontal and vertical scanning directions with the stimulating light, and obtaining the image signal by detecting the photostimulated luminescent light emitted by the scanning, with a solid-state image detector having a photoconductor. The signal, output from the solid-state image detector when scanning a non-image region other than an image recording region on the image recording sheet with the stimulating light, is detected as a correction signal. A non-image component, contained in a signal output from the solid-state image detector when scanning the image recording region with the stimulating light, is suppressed with the correction signal.