A method for reading radiation image information in which a cassette is lowered while keeping each short side of the cassette extending vertically, and then inserted into a radiation image reading apparatus which has a cassette loading inlet in its upper surface and the inserted cassette is taken into the apparatus, and next the front base and the back base are disengaged in the apparatus and both are separated, and after the radiation image information is read from the stimulable phosphor sheet of the back base which are separated from the front base, and then the front base and the back base are joined and ejected from the insertion opening of the apparatus. The apparatus height is smaller than in the method in which the stimulable phosphor sheet is pulled downward from the cassette and is read, and the operation of lifting the cassette against the force of gravity up to the height of the upper surface of the apparatus becomes unnecessary at the time of inserting the cassette.