An exhaust pressure control valve comprises a casing including a bore and a pair of first and second shaft support parts, and a valve shaft placed across the bore and rotatably supported by the shaft support parts. A first end portion of the valve shaft is arranged protruding outside the casing. A throttle valve is secured to the valve shaft inside the bore. An actuator is coupled to the first end portion to open and close the throttle valve. The second shaft support part is located in a bypass passage downstream from a bypass valve and has an opening in which a cap formed with a through hole is fitted. The inside of the second shaft support part is allowed to communicate with atmosphere through the through hole, the bypass passage, and others so that an end face of a second end portion can be subjected to atmospheric pressure.