A computer-controlled laser-beam writing system has been developed for optical integrated circuits (optical ICs). This system allows us to make waveguide patterns 3-4 microm wide, such as directional couplers, and Yjunction, crossed, and S-shaped waveguides, automatically within an edge roughness of 0.2 microm on a photoresist-coated LiNbO(3) substrate. By combining these waveguide patterns, optical ICs can be delineated over more than 50-mm length. This paper presents the system description and the laser-beam writing characteristics of key waveguide patterns. The integrated-optic fiber laser Doppler velocimeter is also demonstrated as an example of large-area optical ICs.