A ball screw device comprising: a threaded shaft ; a nut into which the threaded shaft is inserted having a helical groove that faces a helical groove of the threaded shaft; multiple first balls configured to be rollably arranged on a helical raceway configured by the helical groove of the threaded shaft and the helical groove of the nut; an inner ring raceway groove (16a to 16i) formed on an outer circumferential surface of a portion of the threaded shaft that is a different portion having the helical groove in an axial direction; an outer ring having an outer ring raceway groove (401a to 401i) that faces the inner ring raceway groove (16a to 16i); and multiple second balls configured to be rollably arranged between the inner ring raceway groove (16a to 16i) and the outer ring raceway groove (401a to 401i), wherein the inner ring raceway groove (16a to 16i), the outer ring , and the second balls configure a rolling bearing, and wherein the ball screw device converts rotation of the threaded shaft into linear motion of the nut through the first balls rolling on the helical raceway while being subjected to a load, characterized in that the outer ring has a rolling element insertion hole penetrating from its outer circumferential surface to the outer ring raceway groove (401a to 401i) and a lid configured to cover the rolling element insertion hole , and an inner surface of the lid is formed into a concave shape to serve as part of the outer ring raceway groove (401a to 401i), and in that the outer ring is composed of a cylindrical portion and a flange portion protruding radially outward from the outer peripheral surface of the cylindrical portion in which bolt insertion holes penetrate in the axial direction. a threaded shaft ; a nut into which the threaded shaft is inserted having a helical groove that faces a helical groove of the threaded shaft; multiple first balls configured to be rollably arranged on a helical raceway configured by the helical groove of the threaded shaft and the helical groove of the nut; an inner ring raceway groove (16a to 16i) formed on an outer circumferential surface of a portion of the threaded shaft that is a different portion having the helical groove in an axial direction; an outer ring having an outer ring raceway groove (401a to 401i) that faces the inner ring raceway groove (16a to 16i); and multiple second balls configured to be rollably arranged between the inner ring raceway groove (16a to 16i) and the outer ring raceway groove (401a to 401i), wherein the inner ring raceway groove (16a to 16i), the outer ring , and the second balls configure a rolling bearing, and wherein the ball screw device converts rotation of the threaded shaft into linear motion of the nut through the first balls rolling on the helical raceway while being subjected to a load, characterized in that the outer ring has a rolling element insertion hole penetrating from its outer circumferential surface to the outer ring raceway groove (401a to 401i) and a lid configured to cover the rolling element insertion hole , and an inner surface of the lid is formed into a concave shape to serve as part of the outer ring raceway groove (401a to 401i), and in that the outer ring is composed of a cylindrical portion and a flange portion protruding radially outward from the outer peripheral surface of the cylindrical portion in which bolt insertion holes penetrate in the axial direction. <EOS>