Described is a lock connection device for medical fluid lines (6, 20), comprising a first connector (2) for coupling a first medical fluid line (6) and a second connector (14) for coupling a second medical fluid line (20) wherein both the connectors (2, 14) are adapted for a releasable attachment to each other. The device further comprises a first closing member (26) adapted to be releasably attached to the first connector (2) so as to close it, and a second closing member (30) adapted to be releasably attached to the second connector (14) so as to close it. Further, the first and second closing members (26, 30) are adapted to be attached to each other. In case the first closing member (26) is attached to the first connector (2) and the second closing member (30) is attached to the first closing member (26) and the second connector (14) the first closing member (26) can be detached from the first connector (2) wherein the second closing member (30) remains attached to the first closing member (26) and the second connector (14).
