The Japanese ‘Joint Project’ is a new project to pursue frontiers in particle physics, nuclear physics, materials science, life science and nuclear technology, using a new proton-accelerator complex with the highest beam power in the world. This project had been jointly proposed by the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Research Institution (JAERI), and was approved at the end of 2000. This accelerator complex allows the production of a variety of intense secondary-particle beams such as neutrino, neutron and muon beams. As one of the major facilities in this project, the next generation of a pulsed spallation neutron source with a power of 1 MW will be constructed by the end of 2006, which is comparable to the new pulsed sources realized in the USA and Europe. It can open exciting prospects for materials and life sciences. In this paper, design activities for the new neutron-science facility are summarized.