In an apparatus for optically reading a target based on a light reflected from the target, a light source has a first optical axis and operates to emit light. An imaging optical system has a second optical axis. The imaging optical system is arranged so that the reflected light enters into the imaging optical system. A photodetector has an active area so that the imaging optical system focuses the reflected light on the active area of the photodetector. A light guide member is arranged between the target and the imaging optical system on the first and second optical axes, respectively. The light guide member is configured to guide the light emitted from the light source while preventing the guided light from leaking therefrom to irradiate the guided light to the target.