To provide a check valve that can easily be miniaturized and can prevent retention or remanence of fluid substance therein, and to provide a three-way valve utilizing the check valve and a fluid substance transfer tool.

The check valve 10 includes: a valve element case 11 having a hollow reception chamber 15, an inlet port 17 formed on one side of the reception chamber 15 and an outlet port 19 formed on the other side of the reception chamber 15; and a valve element movable member 13 movably housed between the inlet port 17 and the outlet port 19 in the reception chamber 15. The check valve 10 allows the fluid substance to flow from the inlet port 17 to the outlet port 19. The valve element movable member 13 is provided with penetration channels 14 penetrating from a surface 43 on the side of the inlet port 17 to a surface 44 on the side of the outlet port 19. A closing surface 31 that can make close contact with the penetration channels 14 of the valve element movable member 13 is arranged on the inner wall surface of the reception chamber 15 on the side of the inlet port 17. The penetration channels 14 are closed by bringing the surface 43 of the valve element movable member 13 on the side of the inlet port 17 into contact with the closing surface 31 of the reception chamber 15.