A light guide module of a scanning apparatus includes plural side-emitting light emitting diodes and a light-guiding post, which are disposed on a circuit board. The light-guiding post has plural reflective structures corresponding to respective side-emitting light emitting diodes for receiving light beams from respective side-emitting light emitting diodes. A spacing interval between two of the side-emitting light emitting diodes at a middle portion of the circuit board is greater than a spacing interval between two of the side-emitting light emitting diodes at a side of the circuit board.