Goertler vortices generate in laminar boundary layers on concave walls. The horseshoe vortices generate downstream, and these are broken in laminar-turbulent boundary layers. The experiments were carried out with a concave wall of Im in radius of curvature for 3m/s of main airflow velocity. The behavior of the horseshoe vortices was visualized by smoke and measured with a hot-wire. Additionally, the visualizations and the velocity measurements at four positions were conducted simultaneously. In this paper, the process of the horseshoe vortices breakdown is described.