A hydrogen gas supply device supplies hydrogen gas to a fuel cell stack and includes an electromagnetic pressure regulating valve that regulates the pressure of the hydrogen gas to low pressure. The electromagnetic pressure regulating valve includes a housing, and a valve passage connecting a primary port and a secondary port is formed in the housing. A valve body controls an opening degree of the valve passage and is provided in the housing. A high-pressure sealing member and low-pressure sealing member are provided on an outer periphery of the valve body. The high-pressure sealing member and the low-pressure sealing member are provided in this order from one end side of the valve body to the other end side thereof. The electromagnetic pressure regulating valve further includes a housing pressure equalizing passage connecting the secondary port and a buffer chamber formed between the high-pressure sealing member and the low-pressure sealing member.