An Oxygen Generation System (OGS) is an indispensable system for a long manned space mission. A Solid Polymer Water Electrolysis System (SPWES) has been developing by Kawasaki Heavy Industries, Ltd. for a future space mission since 1985.The authors have been studying the SPWES of a new solid polymer electrolyte with simplified cell structure. We presented the initial study results until 1993 at the former International Conference on Environmental Systems (ICES) shown in REFERENCE. The study was focused on the development of a SPWE cell at ambient pressure. This paper describes a follow-on study results related to development activity of a pressure cell module especially.