To miniaturize the element size of an element (AWG) using an array guide path lattice by partially removing a clad layer at both side portions of a core at the curve portions of multiple guide paths forming the array guide path lattice.

Input/output guide paths 2, 6, star couplers 3, 5 on the input side and output side, and an array guide path lattice section 4 are formed on a guide path substrate 1 having GPSG (quartz glass doped with Ge, P) films as a clad layer and a core layer on the Si substrate 1. A groove forming region 12 forming a groove is provided at the side face section of the core layer at the curve portion of the array guide path lattice section 4. When the wavelength- multiplexed optical signal is introduced from one of input guide paths 2, it is applied with a phase shift corresponding to the optical path difference at the array guide path lattice section 4, and it is separated for each wavelength and outputted to the guide path 6 on the output side via the star coupler 5 on the output side.