An optical bench with improved structure, in which tolerance for misalignment of optical elements becomes great with shortened optical path, the optical bench including a substrate and input and output optical fibers arranged on the substrate with a predetermined separation gap therebetween, where far ends of the input and output optical fibers form a zigzag pattern to guide input and output beams. Input and output optical elements are arranged at the far end of each input and output optical fiber, respectively, condensing and/or diverging the input and output beams. Micro-mirrors receive the input beam from the input optical elements and reflecting the received input beam toward predetermined channels.