A three-way stopcock that can be opened/closed in the same manner as conventional operation methods and can reduce stagnated portions of fluid in a fluid flow passage. Out of branch openings, a first branch opening and a second branch opening are arranged on a straight line, and a third branch opening is directed perpendicularly to the line connecting the first and second branch openings. Provided at a flow passage switch portion are a first flow-passage opening and a second flow-passage opening that are arranged on a straight line and a third flow-passage opening that is directed perpendicularly to the line connecting the first and second bran openings.
