Easy to compact, high yield, and inexpensive three-way stopcock unit, manufacturing costs flowable substance transfer device and a check valve. A second housing which is inserted with the first housing having a valve seat opening is provided in the housing of said first check valve according to the three-way stopcock unit of the present invention, the valve housing of said first I and a valve body which is sandwiched between the open end of the housing and said second seat. Inside of the inner periphery of the housing of the second valve body is provided with a cut substantially U-shaped and outside of the outer peripheral edge of the opening formed in the valve seat of the first housing. The inner portion of the cut is used as an opening and closing valve, and the open end of the housing and the second valve seat of the first housing is closed in a liquid tight state with the outer portion of the cut.小型化し易く、歩留まりが高く、且つ、製造コストが安価な三方活栓ユニット、逆止弁及び流動性物質移送装置。本発明の三方活栓ユニットに係る逆止弁は、開口が設けられた弁座を有する第一のハウジングと、該第一のハウジングに挿入される第二のハウジングと、該第一のハウジングの弁座と該第二のハウジングの開口端部とに挟持される弁体とを備える。弁体は、第一のハウジングの弁座に設けられた開口の外周縁部よりも外側で且つ第二のハウジングの内周縁部よりも内側に、略U字状の切れ目が設けられる。そして、切れ目の内側部分が開閉弁として使用され、且つ、切れ目の外側部分で第一のハウジングの弁座と第二のハウジングの開口端部とが液密状態に閉塞される。
