To provide a relief valve not having a portion slidably moving according to the operation of a valve element.

This relief valve 3 comprises the valve element 13, a valve seat 12 having a seat face 12s seated by the valve element 13 and a body 1b in which a first inner hole h1 to which the valve seat 12 is fixed is formed. The pressure of a fluid is kept constant by discharging the fluid to the outside since the valve element 13 is separated from the seat face 12s of the valve seat 12 when the pressure of the fluid acting on the valve element 13 exceeds a specified pressure. A magnet 13m is fixed to the valve element 13, a magnet plate 14 mutually exerting a magnetic force on the magnet 13m is fixed to the second inner hole h2 of the body 1b, and the valve element 13 is energized to the seat face 12s of the valve seat 12 by the magnetic force acting between the magnet 13m and the magnet plate 14.