Cooling water direct injection type fuel cell

A cooling water direct injection type fuel cell is provided. The fuel cell includes an air-side separator that has an air channel through which air flows, and a cooling water inlet aperture that is formed on an introduction portion of the air channel. A hydrogen-side separator is joined with the air-side separator and has a protrusion that is inserted into the cooling water inlet aperture. The protrusion has a diameter less than a diameter of the cooling water inlet aperture to form a gap between an outer circumferential surface of the protrusion and an inner circumferential surface of the cooling water inlet aperture. Cooling water drawn into space between the junction surfaces of the air-side separator and the hydrogen-side separator is discharged through the gap between the protrusion and the cooling water inlet aperture, is mixed with introduced air, and then is drawn into the air channel.