The magnetization response of a thin film head was studied using high-frequency micro-Kerr system. This system has a frequency response up to 50 MHz and is able to measure magnetization changes. A laser spot size is about 0.5μm in diameter. An amplitude of magnetization changes at the center of the pole increased as a frequency increased, though it was not so at an edge of the pole. A phase shift at the edge of the pole is larger than that at the center of the pole. These phenomena seem to be caused by the eddy current distribution of the magnetic pole.