A connector (10) comprises, inside a main body (38), first to third ports (24, 26, 28) having a fluid passage through which an infusion agent can flow in or flow out, an inner fluid passage (52) which communicates between the fluid passages of the first port (24) and the second port (26), and a through hole (76) which is connected to the inner fluid passage (52). On the inner fluid passage (52), an upstream side wall face (92) is provided which is capable of guiding the infusion agent that flows into the inner fluid passage (52) from the first port (24) to the through hole (76) and which makes the cross sectional area of the infusion agent fluid passage near the through hole (76) narrower than the cross sectional area of the first port (24).
