A check valve comprising: a valve seat member (21, 31) provided with a fluid circulation port (15, 30); a plate-shaped valve member (22, 33) provided on a downstream side of the valve seat member (21, 31) and configured to open/close the circulation port (15, 30); a spring (23, 34) provided on a downstream side of the valve member (22, 33) and configured to bias the valve member (22, 33) toward the circulation port (15, 30); a spring receiving member (24, 35) provided for the spring (23, 34) on a downstream side thereof; an attachment member that includes an insertion member and a threadedly-engagement member, wherein the attachment member is for attaching the valve seat member and the valve member to a discharge pipe; and a plurality of circular guide rods (25, 36) provided at a periphery of the valve member (22, 33) and formed to extend in an upstream-to-downstream flow direction, each having a downstream end portion attached to the spring receiving member (24, 35), and each being inserted into an insertion hole formed at the valve seat member, and then, being fastened and attached to a screw hole formed at the insertion member, and configured to contact an outer peripheral surface of the valve member (22, 33), and guide the valve member (22, 33) in the upstream-to-downstream flow direction, the check valve being provided at the discharge pipe of a drain funnel, wherein an upstream end portion of each guide rod (25, 36) is inserted into a periphery of the circulation port (15, 30) of the valve seat member (21, 31), the spring receiving member (24, 35) is formed in a substantially discoid shape, and provided with a recess (24a, 35a) formed at a center thereof, into which a downstream end portion of the spring (23, 34) is inserted, and an external thread portion is formed at the downstream end portion of each guide rod (25, 36), and the spring receiving member (24, 35) is fixed with nuts (26, 37) with the downstream end portion of each guide rod (25, 36) being inserted into the spring receiving member (24, 35). a valve seat member (21, 31) provided with a fluid circulation port (15, 30); a plate-shaped valve member (22, 33) provided on a downstream side of the valve seat member (21, 31) and configured to open/close the circulation port (15, 30); a spring (23, 34) provided on a downstream side of the valve member (22, 33) and configured to bias the valve member (22, 33) toward the circulation port (15, 30); a spring receiving member (24, 35) provided for the spring (23, 34) on a downstream side thereof; an attachment member that includes an insertion member and a threadedly-engagement member, wherein the attachment member is for attaching the valve seat member and the valve member to a discharge pipe; and a plurality of circular guide rods (25, 36) provided at a periphery of the valve member (22, 33) and formed to extend in an upstream-to-downstream flow direction, each having a downstream end portion attached to the spring receiving member (24, 35), and each being inserted into an insertion hole formed at the valve seat member, and then, being fastened and attached to a screw hole formed at the insertion member, and configured to contact an outer peripheral surface of the valve member (22, 33), and guide the valve member (22, 33) in the upstream-to-downstream flow direction, the check valve being provided at the discharge pipe of a drain funnel, wherein an upstream end portion of each guide rod (25, 36) is inserted into a periphery of the circulation port (15, 30) of the valve seat member (21, 31), the spring receiving member (24, 35) is formed in a substantially discoid shape, and provided with a recess (24a, 35a) formed at a center thereof, into which a downstream end portion of the spring (23, 34) is inserted, and an external thread portion is formed at the downstream end portion of each guide rod (25, 36), and the spring receiving member (24, 35) is fixed with nuts (26, 37) with the downstream end portion of each guide rod (25, 36) being inserted into the spring receiving member (24, 35). provided at a periphery of the valve member (22, 33) and formed to extend in an upstream-to-downstream flow direction, each having a downstream end portion attached to the spring receiving member (24, 35), and each being inserted into an insertion hole formed at the valve seat member, and then, being fastened and attached to a screw hole formed at the insertion member, and configured to contact an outer peripheral surface of the valve member (22, 33), and guide the valve member (22, 33) in the upstream-to-downstream flow direction, the check valve being provided at the discharge pipe of a drain funnel, wherein an upstream end portion of each guide rod (25, 36) is inserted into a periphery of the circulation port (15, 30) of the valve seat member (21, 31), the spring receiving member (24, 35) is formed in a substantially discoid shape, and provided with a recess (24a, 35a) formed at a center thereof, into which a downstream end portion of the spring (23, 34) is inserted, and an external thread portion is formed at the downstream end portion of each guide rod (25, 36), and the spring receiving member (24, 35) is fixed with nuts (26, 37) with the downstream end portion of each guide rod (25, 36) being inserted into the spring receiving member (24, 35).