A relief valve (10, 10W, 10X) comprising: a bolt-type valve body; a hollow room which is formed in a center portion of the bolt-type valve body and which includes a component insertion port that is open to an end surface of a head portion of the bolt-type valve body; a lid member which closes the component insertion port; a valve hole which is open to a tip end surface of the bolt-type valve body and which communicates with the hollow room; a valve member which is accommodated in the hollow room and which opens and closes the valve hole; an elastic member which is accommodated in the hollow room and which biases the valve member to a side where the valve hole is closed; a cylindrical portion which is formed in the lid member and which protrudes from the end surface of the head portion; a plurality of discharge holes; and a direction change member (45, 45W, 45X) which is rotatingly operated and which changes a direction in which a discharge hole is open to an arbitrary direction, wherein the discharge holes are formed in a plurality of positions on the side surface of the cylindrical portion, and wherein the relief valve (10, 10W, 10X) includes: a cover member (45, 45W, 45X) which is rotatably fitted in an outer side of the cylindrical portion, which closes part of the plurality of discharge holes and which serves as the direction change member (45, 45W, 45X); and an opening open portion (47, 47W) which is formed in the cover member (45, 45W, 45X) and which opens the arbitrary discharge holes according to a rotation position of the cover member (45, 45W, 45X), characterized in that the relief valve further comprises a locking protruding portion which is formed in the cover member (45, 45W, 45X) and which is locked into a discharge hole. a bolt-type valve body; a hollow room which is formed in a center portion of the bolt-type valve body and which includes a component insertion port that is open to an end surface of a head portion of the bolt-type valve body; a lid member which closes the component insertion port; a valve hole which is open to a tip end surface of the bolt-type valve body and which communicates with the hollow room; a valve member which is accommodated in the hollow room and which opens and closes the valve hole; an elastic member which is accommodated in the hollow room and which biases the valve member to a side where the valve hole is closed; a cylindrical portion which is formed in the lid member and which protrudes from the end surface of the head portion; a plurality of discharge holes; and a direction change member (45, 45W, 45X) which is rotatingly operated and which changes a direction in which a discharge hole is open to an arbitrary direction, wherein the discharge holes are formed in a plurality of positions on the side surface of the cylindrical portion, and wherein the relief valve (10, 10W, 10X) includes: a cover member (45, 45W, 45X) which is rotatably fitted in an outer side of the cylindrical portion, which closes part of the plurality of discharge holes and which serves as the direction change member (45, 45W, 45X); and an opening open portion (47, 47W) which is formed in the cover member (45, 45W, 45X) and which opens the arbitrary discharge holes according to a rotation position of the cover member (45, 45W, 45X), characterized in that the relief valve further comprises a locking protruding portion which is formed in the cover member (45, 45W, 45X) and which is locked into a discharge hole. a cover member (45, 45W, 45X) which is rotatably fitted in an outer side of the cylindrical portion, which closes part of the plurality of discharge holes and which serves as the direction change member (45, 45W, 45X); and an opening open portion (47, 47W) which is formed in the cover member (45, 45W, 45X) and which opens the arbitrary discharge holes according to a rotation position of the cover member (45, 45W, 45X), characterized in that the relief valve further comprises a locking protruding portion which is formed in the cover member (45, 45W, 45X) and which is locked into a discharge hole.