We performed a gamma ray generation experiment by means of reflecting laser photons off high energy electron beams (laser-Compton scattering) for the development of a polarized positron source of the International Linear Collider (ILC). The ILC is the project to build a 30 km long linear accelerator to search for new phenomena or explore the origin of the universe via electron-position interactions. In electron-positron interactions, the accuracy of measurements can be remarkably improved by using polarized beam, the ILC plans to use polarized electron beams. In addition, it is desirable to use polarized positron beams in order further to improve performance of the facility.……