The magnetization response of thin film heads in the high frequency region was studied using a scanning Kerr effect microscope. The area of large magnetization rotation converges gradually to the central region of the core of a thin film head as the frequency is increased. Above 20 MHz, the domain structure changes, i.e. the number of domains increases with increasing frequency and there is less curvature at both sides of the 180?? walls. As a result, the region of convergence of the magnetization rotation broadens. Comparing the static magnetization direction and the magnetization response, it was found that at high frequencies the magnetization in the track direction goes through large rotations, while that inclined from the track direction undergoes only small rotations.