To provide a three-way valve having a small fluid resistance, easy to set a flow characteristic, making the valve element opening/closing force small, and nevertheless capable of promoting a smaller size of the valve element and valve box and establishing a lightweight construction and a reduced manufacturing cost.

A fixed wall 9 protruding toward the first flow passage axis X1 in such a condition as partitioning a second flow passage W2 and a third flow passage W3 is formed continuously on the inner wall surface in the passage connecting part of the valve box 7 where the first to third passage W1-W3 are formed in communication ion a T-shape and at the boundary between the second W2 and third passages W3 or in its neighbouring part, and in the forefront of the fixed wall 9, a swinging base end 8A of the valve element 8 is installed in the condition to make slide contacting therewith.