To provide a technology for securing a tool margin for connecting to a connecting object member in a gas-liquid separator.

This is a gas-liquid separator used for a fuel cell system having a fuel cell, and is provided with a separation section which separates a fuel gas after supplied for electrochemical reaction in the fuel cell and liquid water flowing together with the fuel gas, a storage section for storing water discharged from the fuel cell, and a fluid leading-out passage which has a fluid leading-out port connected to a connection object member and is formed toward perpendicular direction and leads out the fluid in the gas-liquid separator to the connecting object member through the fluid leading-out port and in which the fluid leading-out port is installed at a position shifted in vertical direction to the separation section and the storage section.