To provide a check valve in which when fluid pressure of an inlet becomes larger than fluid pressure of an outlet and energization force of a coil spring, a disk-shaped valve body compresses the coil spring and can be separated from an annular valve seat.

An inlet 1, a valve chamber 5 and an outlet 3 are formed by a valve casing composed of an inlet side member 2 and an outlet side member 4. A metallic annular valve seat 6 is arranged between the inlet 1 and the valve chamber 5. A disk-shaped valve body 7 in which a portion to be seated/separated on/from the annular valve seat 6 is composed of a rubber-made rubber part 7a is arranged in the valve chamber 5. A coil spring 8 energizes the disk-shaped valve body 7 to the annular valve seat 6. By forming a projection part 7b with a semicircular section on a tip part of the rubber part 7a of the disk-shaped valve body 7 to be seated/separated on/from the annular valve seat 6, a contact area between the disk-shaped valve body 7 and the annular valve seat 6 can be reduced.