PURPOSE: To make coupling loss less and manufacture easy by emitting polymn. light to a coupling part to obtain high refractive index layers, irradiating fixing light thereto to obtain condensing means and coupling optical waveguides and optical transmission means by said condensing means.

CONSTITUTION: An optical fiber 16 for input and optical fibers 17, 18 for output are placed on a plastic substrate 10, and a polymn. liquid is flowed to form a polymer film layer 11 united to each fiber. A glass mask having a pattern for optical waveguides is superposed thereon and polymn. light is irradiated thereto to form the core parts for the optical waveguides. When the polymn. light is made incident to the fiber 16, high refractive index layers 22, 23, 24, 25, 26 are formed. As a result, waveguide type lenses 19a, 19b, 19c are formed by said high refractive index layers. When the lenses 19aW19c are formed, UV light is irradiated over the entire part of the film 11 to fix and stabilize the same. The optical waveguides, the fibers 16W18 and condensing means 19aW19c are thus united to one body and an optical transmission coupler is perfected.