To consider swinging of conductor under strong wind condition is important for design of tower. Especially cost increase and harmful visual impression is caused at long span in order to increase in size of tower so that conductor may not contact each other. The authors have proposed numerical analysis method based on computer simulation “CAFSS” for calculating conductor’s swinging. Its excellent performance was confirmed the theoretically and experimentally by comparing analysis for observation swinging on test lines in a typhoon with results of “CAFSS” by using observation wind. This paper presents the comparison of conductor for swinging between “CAFSS” and observation in Miyakojima test line constructed in flat terrain.