An image reading apparatus includes a casing having a side panel which has a cassette loading slot defined therein for loading a cassette therein. A stimulable phosphor sheet stored in the cassette loaded in the cassette loading slot is removed from the cassette and fed vertically downwardly along a first vertical feed path. Radiation image information recorded in the stimulable phosphor sheet is read by a reader. Thereafter, the stimulable phosphor sheet is stored back into the cassette, which is then delivered toward a cassette unloading slot by a sliding displacement mechanism. The stimulable phosphor sheet is removed again from the cassette, and fed along a second vertical feed path for an eraser to erase remaining radiation image information from the stimulable phosphor sheet.