An infusion set for engagement with a female connector, the infusion set comprising: a first flow channel that is constituted by a pliable tube and includes a spike provided at one end thereof a second flow channel that is constituted by a pliable tube and includes a lock connector provided at one end thereof a third flow channel that is constituted by a pliable tube (30a, 30b, 30c); and a three-way stopcock to which another end of the first flow channel, another end of the second flow channel and another end of the third flow channel are connected, wherein the three-way stopcock includes a handle that can be switched between a first position and a second position, the first position being a position that brings the first flow channel and the third flow channel into communication with each other, wherein the second flow channel is not in communication with the first flow channel and the third flow channel; and the second position being a position that brings the second flow channel and the third flow channel into communication with each other; characterised in that: the lock connector includes a lock mechanism (52, 60, 65) that in use is brought into engagement with the female connector; the third flow channel includes a male connector provided at one end thereof; in the second position, the first flow channel is not in communication with the second flow channel and the third flow channel; and the three-way stopcock is configured such that the handle cannot be pivoted to a third position that brings the first flow channel, the second flow channel and the third flow channel into communication with each other. a first flow channel that is constituted by a pliable tube and includes a spike provided at one end thereof a second flow channel that is constituted by a pliable tube and includes a lock connector provided at one end thereof a third flow channel that is constituted by a pliable tube (30a, 30b, 30c); and a three-way stopcock to which another end of the first flow channel, another end of the second flow channel and another end of the third flow channel are connected, wherein the three-way stopcock includes a handle that can be switched between a first position and a second position, the first position being a position that brings the first flow channel and the third flow channel into communication with each other, wherein the second flow channel is not in communication with the first flow channel and the third flow channel; and the second position being a position that brings the second flow channel and the third flow channel into communication with each other; characterised in that: the lock connector includes a lock mechanism (52, 60, 65) that in use is brought into engagement with the female connector; the third flow channel includes a male connector provided at one end thereof; in the second position, the first flow channel is not in communication with the second flow channel and the third flow channel; and the three-way stopcock is configured such that the handle cannot be pivoted to a third position that brings the first flow channel, the second flow channel and the third flow channel into communication with each other. the lock connector includes a lock mechanism (52, 60, 65) that in use is brought into engagement with the female connector; the third flow channel includes a male connector provided at one end thereof; in the second position, the first flow channel is not in communication with the second flow channel and the third flow channel; and the three-way stopcock is configured such that the handle cannot be pivoted to a third position that brings the first flow channel, the second flow channel and the third flow channel into communication with each other.