Disclosed is a clamp (64) including: a protrusion section (144) which presses a first tube (56)； a locking section (140) having a first engagement section (150) and a second engagement section (152) that form therebetween an engagement groove (154) in which the protrusion section (144) is inserted and by which engagement can be made； a first engagement release section (156) which releases an engaged state between the first engagement section (150) and the protrusion section (144)； and a second engagement release section (158) which releases an engaged state between the second engagement section (152) and the protrusion section (144). Also disclosed is a blood bag system (10) including the clamp (64).
