In an optical tap module, a first lens, a focusing lens, and a photodiode are arranged such that a center axis of a cylindrical case housing the first lens, the focusing lens, and the photodiode is substantially located on the same line. When light propagates through a second optical fiber and is emitted from an end surface facing the first lens so as to be incident on an optical filter, and light transmitted the optical filter is converged by the focusing lens, the photodiode and a chip mounting support are arranged such that a focal point of light is located spatially distant from the surfaces of the photodiode and the chip mounting support.