To manufacture a composite base on which holes of accurate pitches and accurate bores are formed and functional parts such as a lenses and others are embedded into the holes with a high accuracy.

A resist pattern is formed on a dummy base 10 by lithography, and then a solid film such as alumina or the like (a first base; a first solid film) 12 is applied on the whole face of the resist pattern. The whole of the base is ground smoothly and photoresists appeared on the surface are removed to form accurate fitting holes 12a. A reinforcing base (a second base; a second solid film) 14 with rough holes 14a larger than the fitting holes 12a and also larger than spherical lenses 15 is disposed on the position whereon the fitting holes 12a and the rough holes 14a are faced each other and integrated thereon. The dummy base 10 is melt removed, and then the spherical lenses 15 are inserted into the rough holes 14a, and their lower ends are fitted into the fitting holes 12a, and their peripheries are sealed with glass 16 and the spherical lenses 15a are fixed on the fitting holes 12a.