Alkaline electrolysis (ALK) and proton exchange membrane (PEM) water electrolysis are two prominent commercialized electrolysis technologies, each offering advantages of low initial installation cost and high efficiency. The Korea Research Institute of Chemical Technology is actively involved in intensive research and development of separation membranes for various electrolysis technologies. The presentation introduces the current status of ALK electrolysis diaphragms and PEM electrolysis membranes. The first part highlights a highly selective diaphragm that suppresses hydrogen permeation in ALK electrolysis, achieving a hydrogen permeation rate of less than 1/10 and resistance of less than 1/2 compared to conventional diaphragms. In the second part, the research focuses on graft electrolyte membranes to enhance PEM electrolysis performance, resulting in a unique microstructure with distinct hydrophilic-hydrophobic domains and excellent ion conductivity and reduced hydrogen permeation rate compared to Nafion.