An apparatus for generating an image may include a plurality of scintillator layers configured to convert an incident beam into an optical signal; a plurality of micro cells configured to turn on or off depending on whether or not the micro cells detect the optical signal; a reaction depth determining unit configured to detect a decay pattern of the optical signal, on the basis of on/off signals of the micro cells, and configured to determine a type of the scintillator layers with which the incident beam has reacted; and/or a reading unit configured to decide an occurrence location of the incident beam and then generates a photographed image.