Exhaust passage control valve 10 may comprise housing 30, valve member 20, and helical torsion spring 40. Housing 30 has an exhaust passage. Exhaust gas from an internal combustion engine flows through the exhaust passage of the housing 30. Valve member 20 opens and closes the exhaust passage of the housing. Helical torsion spring 40 may be disposed at the opposite side of the valve member from the housing side thereof. Helical torsion spring 40 comprises a coil part wherein spring wires have been wound in a coil shape, and arms formed at both ends of the coil part. The coil part may be disposed at approximately the center of the valve member. When the arms bend with respect to the coil part, the counter-force of this bending energizes the valve member towards a closing side. The spring mounting member may be arranged and constructed to adjust a position in which the spring mounting member is mounted on the housing such that a rotation angle of the arms can be changed.