Recently, many researches on migrating fish have been conducted for study on fish biology. Ordinarily, counting methods of fish in fishways are relied on visual counting from shore, or trap counting; however, the development of a system which allows counting in long period of time is in exigent. An automatic counting system with CCD line-camera is developed to meet the necessity. The camera takes a series of images of fish passing through fishway and the images are converted into digital information to count fishes automatically. In this article, an outline of the system, result of experiments, and subjects to be considered are mentioned.