The ongoing research and development of sunlight-driven water splitting in the “Japan Technological Research Association of Artificial Photosynthetic Chemical Process (ARPChem)” is overviewed. Water splitting photocatalysts, photoelectrochemical devices, large-scale reactor panels, product gas transportation, H₂/O₂ gas separation devices and safety measures against explosion are included as the research objectives. ARPChem was formed as a research union of Japan’s leading chemical firms, in which related elementary technologies have been cultivated. This article introduces our general scope for artificial photosynthesis and describes present research activities, mainly on solar driven water splitting photocatalysts/photoelectrodes and briefly on the processes and plans for plant construction for future industrial extension.