The present invention is directed to a connector with which negative pressure in the channel space in the connector can be prevented during luer removal, in a closed-system connector..A slit (49) is furnished in valve body (40) of three-way stopcock (100). During luer access and luer removal, first and second moving parts (M1) and (M2) to the left and right of slit (49) enter and withdraw from first and second valve body accommodating chambers (51) and (52), respectively. First and second valve body accommodating chambers (51) and (52) are formed outside of channel space (S), so the operation whereby first and second moving parts (M1) and (M2) enter and withdraw during luer access and luer removal does not affect the change in volume of channel space (S) and negative pressure can be prevented from occurring in channel space (S) by the aforementioned entry, and withdrawal.
