An exhaust valve device for a fuel tank includes a casing partitioning an inside into an upper chamber and a lower chamber by a bulkhead including a through hole, an inflow hole communicating the lower chamber and an inside of the fuel tank, an exhaust hole communicating a side portion of the upper chamber and an outside of the fuel tank, and a float valve displaceably supported in the lower chamber. A portion defining the upper chamber of the casing includes a cylinder portion and a circular plate closing an upper end of the cylinder portion. A buffer chamber is defined between the cylinder body and the bulkhead to communicate with the lower chamber by the through hole. In a side wall on a side opposing an exhaust hole side of the cylinder body, a first ventilation hole communicating the buffer chamber and the upper chamber is formed.