A radiation image read-out method includes obtaining an image signal, which represents a radiation image, from a solid-state radiation detector constituted of a plurality of solid-state detecting devices for detecting radiation, which are arrayed in a matrix-like form along a main scanning direction and a sub-scanning direction and each of which corresponds to one pixel. A pixel density transforming process is performed on the image signal and in accordance with a pixel size, which is determined in accordance with a desired image size in cases where read-out processing is performed with respect to different image sizes, a read-out density of a solid-state radiation detector need not be altered, but the method can cope with narrowness of an allowable width of the number of pixels in an image reproducing apparatus or an image filing apparatus.