Protein crystal growth experiment in space has been performed for more than 20 years. Although microgravity was expected to affect crystallization process to crystals of better quality, it could not meet the expectation of the contribution to structural biology. JAXA has conducted the High-quality Protein Crystal Growth Experiment project on International Space Station since 2002. In this project, international cooperation with Federal Space Agency of Russia and European Space Agency is an important key factor for success of the experiment. We introduce this unique project and details of international cooperation.