A drug container connector (1; 2) comprising: a puncture needle capable of puncturing a plug that seals a mouth of a container ; and a cover (90; 290) that covers an opening , on a tip side, of a flow channel through which liquid flows and that is formed in the puncture needle, the puncture needle being configured to penetrate the cover and puncture the plug, wherein the puncture needle is provided on a connector main body (10; 210), the cover is held by a slider (50; 250), and the slider is movable with respect to the connector main body in a longitudinal direction of the puncture needle, characterised in that : the slider is provided with a claw capable of engaging with a flange at the mouth of the container, wherein, when the slider is in an initial position where the slider is drawn to a maximum out of the connector main body, the opening of the puncture needle is stored in the cover without being exposed to the outside, wherein the drug container connector comprises a lock mechanism for preventing disengagement between the claw and the flange, and the lock mechanism comprises: a grip arm on which the claw is formed and that can elastically bend and deform outwardly; and the connector main body (10; 210), which is configured to prevent the grip arm from bending and deforming outwardly in a state in which the slider (50; 250) is stored in the connector main body (10; 210). a puncture needle capable of puncturing a plug that seals a mouth of a container ; and a cover (90; 290) that covers an opening , on a tip side, of a flow channel through which liquid flows and that is formed in the puncture needle, the puncture needle being configured to penetrate the cover and puncture the plug, wherein the puncture needle is provided on a connector main body (10; 210), the cover is held by a slider (50; 250), and the slider is movable with respect to the connector main body in a longitudinal direction of the puncture needle, characterised in that : the slider is provided with a claw capable of engaging with a flange at the mouth of the container, wherein, when the slider is in an initial position where the slider is drawn to a maximum out of the connector main body, the opening of the puncture needle is stored in the cover without being exposed to the outside, wherein the drug container connector comprises a lock mechanism for preventing disengagement between the claw and the flange, and the lock mechanism comprises: a grip arm on which the claw is formed and that can elastically bend and deform outwardly; and the connector main body (10; 210), which is configured to prevent the grip arm from bending and deforming outwardly in a state in which the slider (50; 250) is stored in the connector main body (10; 210). the slider is provided with a claw capable of engaging with a flange at the mouth of the container, wherein, when the slider is in an initial position where the slider is drawn to a maximum out of the connector main body, the opening of the puncture needle is stored in the cover without being exposed to the outside, wherein the drug container connector comprises a lock mechanism for preventing disengagement between the claw and the flange, and the lock mechanism comprises: a grip arm on which the claw is formed and that can elastically bend and deform outwardly; and the connector main body (10; 210), which is configured to prevent the grip arm from bending and deforming outwardly in a state in which the slider (50; 250) is stored in the connector main body (10; 210). <EOS>