A reed valve 1 includes: a valve body 4; a valve seat 6 having a valve hole 3 for passage of a fluid J; a casing 8 accommodating the valve body 4; and a reed 10 including an arm part 18 having a first end portion 22 connected to the casing 8, and a valve body support part 20 connected to a second end portion 24 of the arm part 18 and supporting the valve body 4 so that the valve hole 3 can be opened and closed. When a first direction D1 is a flow direction of the fluid J in the valve hole 3, and a first surface 21 is a surface facing downstream in the first direction D1 among an inner surface of the casing 8, the first surface 21 includes a recess 27 facing the arm part 18.