A method for fabrication of a multilayered optical waveguide structure which includes at least two substrates, and an optical waveguide layer disposed between the substrates and having at least one core region and side cladding regions laterally succeeding from the core region. The method is characterized in that the optical waveguide layer is formed from a polysilane compound containing polysilane, and it comprises stacking a first block including one of the substrates and a second block including the other of the substrates through the optical waveguide layer or a cladding layer located at a surface of either one of the blocks, and heating them while pressed in such arrangement so that the first block and the second block are bonded together by the optical waveguide layer or the cladding layer serving as a bonding layer into the multilayered structure.