A three-port valve comprising: a first elastic tube through which fluid flows; a first port (2a1) arranged as a port for feed and exhaust in the first elastic tube; a second elastic tube through which the fluid flows; a second port (2b1) arranged as a port for feed and exhaust in the second elastic tube; a third port which communicates with the first port (2a1) and the second port (2b1); a first flow control means (6a, 7a, 8a) including a first compressing spring and a first movable element through which the first elastic tube is arranged, and controlling flow of the fluid through the first elastic tube by moving the first movable element outward in a direction of elasticity of the first compressing spring so as to deform the first elastic tube; a second flow control means (6b, 7b, 8b) including a second compressing spring and a second movable element through which the second elastic tube penetrates, and controlling flow of the fluid through the second elastic tube by moving the second movable element outward in a direction of elasticity of the second compressing spring so as to deform the second elastic tube; and a swinging element which drives the first flow control means (6a, 7a, 8a) and the second flow control means (6b, 7b, 8b); wherein a set of the first elastic tube and the first flow control means (6a, 7a, 8a) and a set of the second elastic tube and the second flow control means (6b, 7b, 8b) are symmetrically arranged with respect to the swinging element; characterized in that a first set screw which adjusts a flow rate by being moved toward the swinging element in the direction of elasticity of the first compressing spring against elastic force of the first compressing spring so as to deform the first elastic tube arranged through the first movable element, independently of driving of the swinging element; and a second set screw which adjusts a flow rate by being moved toward the swinging element in the direction of elasticity of the second compressing spring against elastic force of the second compressing spring so as to deform the second elastic tube arranged through the second movable element, independently of the driving of the swinging element. a first elastic tube through which fluid flows; a first port (2a1) arranged as a port for feed and exhaust in the first elastic tube; a second elastic tube through which the fluid flows; a second port (2b1) arranged as a port for feed and exhaust in the second elastic tube; a third port which communicates with the first port (2a1) and the second port (2b1); a first flow control means (6a, 7a, 8a) including a first compressing spring and a first movable element through which the first elastic tube is arranged, and controlling flow of the fluid through the first elastic tube by moving the first movable element outward in a direction of elasticity of the first compressing spring so as to deform the first elastic tube; a second flow control means (6b, 7b, 8b) including a second compressing spring and a second movable element through which the second elastic tube penetrates, and controlling flow of the fluid through the second elastic tube by moving the second movable element outward in a direction of elasticity of the second compressing spring so as to deform the second elastic tube; and a swinging element which drives the first flow control means (6a, 7a, 8a) and the second flow control means (6b, 7b, 8b); wherein a set of the first elastic tube and the first flow control means (6a, 7a, 8a) and a set of the second elastic tube and the second flow control means (6b, 7b, 8b) are symmetrically arranged with respect to the swinging element; characterized in that a first set screw which adjusts a flow rate by being moved toward the swinging element in the direction of elasticity of the first compressing spring against elastic force of the first compressing spring so as to deform the first elastic tube arranged through the first movable element, independently of driving of the swinging element; and a second set screw which adjusts a flow rate by being moved toward the swinging element in the direction of elasticity of the second compressing spring against elastic force of the second compressing spring so as to deform the second elastic tube arranged through the second movable element, independently of the driving of the swinging element.