In a relief valve device, a positive-pressure relief valve opens a first valve port when pressure in a pressure chamber increases to a pressure that is equal to or higher than positive-pressure side valve-opening pressure. A negative-pressure relief valve opens a second valve port when pressure in the pressure chamber decreases to a pressure that is equal to or lower than negative-pressure side valve-opening pressure. When the positive-pressure relief valve is closed, a positive valve-opening pressure adjustment unit adjusts a set load of a positive-pressure spring according to an amount of an adjustment screw screwed in the pedestal plate. When the negative-pressure relief valve is closed, a negative valve-opening pressure adjustment unit adjusts a set load of the negative-pressure spring via the valve plate through forward or backward movement of the pedestal plate relative to a housing main body.