To provide a method for quality guarantee of a system for reading out a radiation image by carrying out linear scanning of a photo-stimulable phosphor face exposed to the radiation image.

Reading out of a stored image in a photo stimulable phosphor face is carried out by scanning the screen using stimulating light beam 8 emitted from a light source 9 and having a wavelength within a range of wavelength with which the used phosphor body is stimulated. High speed scanning movement can be obtained by radiating light beam 8 emitted from a laser toward a galvanometer mirror 10. Low speed scanning movement is carried out using a means to transfer the image at uniform speed in the vertical direction to the main scanning direction in order to scan the whole sheet evenly (in the direction shown as an arrow). Electric signals are converted into digital signals by a square wave amplifier and an analog-to-digital converter and the digital signals are then sent to an image processing module of a reading out apparatus and stored in a memory disk of the system.