A rotating electrical machine, comprising: a rotating electrical machine main body having a stator, a rotor disposed opposing the stator and rotating with an axial line of a rotating shaft as a center, a fan provided on an axial line direction end portion of the rotor, and a frame that supports the stator and the rotor; a rectifying device attached to the rotating electrical machine main body on an outer side in the axial line direction of the rotating electrical machine main body; and a cover attached to the rotating electrical machine main body and covering the rectifying device, wherein the rectifying device has a plate-form first rectifying unit provided on the cover side, a plate-form second rectifying unit provided on a frame side, and a plate-form circuit board provided between the first rectifying unit and the second rectifying unit, and radial direction outer side sizes of the second rectifying unit, the circuit board, and the first rectifying unit are formed so as to be sequentially smaller in a direction away from the frame, and are disposed at predetermined intervals, the cover is formed of a cover end wall portion positioned farther to the outer side in the axial line direction than the rectifying device, a cover outer wall portion positioned farther to the outer side in the radial direction than the rectifying device, and a cover intermediate portion interposed between the cover end wall portion and the cover outer wall portion, an inner peripheral side inlet portion having an inlet hole is formed in the cover end wall portion, an outer peripheral side inlet portion having an inlet hole (635, 636) is formed in the cover intermediate portion, and the outer peripheral side inlet portion has a radial direction covering portion existing in a position nearer the frame in the axial line direction than the cover end wall portion, and an axial direction covering portion that connects the radial direction covering portion and an outer peripheral portion of the cover end wall portion, one portion of circumferential ribs configuring an inlet port of the axial direction covering portion is positioned farther to the outer side in the axial line direction than a gap between the circuit board and the first rectifying unit, and one portion of circumferential ribs configuring an inlet port of the radial direction covering portion is positioned farther to the outer side in the axial line direction than a gap between the circuit board and the second rectifying unit, wherein a cross section of the one portion of circumferential ribs configuring the inlet port of the radial direction covering portion and a cross section of the one portion of circumferential ribs configuring the inlet port of the axial direction covering portion are of a rectangular form having a plane parallel to the radial direction of the rotating shaft. a rotating electrical machine main body having a stator, a rotor disposed opposing the stator and rotating with an axial line of a rotating shaft as a center, a fan provided on an axial line direction end portion of the rotor, and a frame that supports the stator and the rotor; a rectifying device attached to the rotating electrical machine main body on an outer side in the axial line direction of the rotating electrical machine main body; and a cover attached to the rotating electrical machine main body and covering the rectifying device, wherein the rectifying device has a plate-form first rectifying unit provided on the cover side, a plate-form second rectifying unit provided on a frame side, and a plate-form circuit board provided between the first rectifying unit and the second rectifying unit, and radial direction outer side sizes of the second rectifying unit, the circuit board, and the first rectifying unit are formed so as to be sequentially smaller in a direction away from the frame, and are disposed at predetermined intervals, the cover is formed of a cover end wall portion positioned farther to the outer side in the axial line direction than the rectifying device, a cover outer wall portion positioned farther to the outer side in the radial direction than the rectifying device, and a cover intermediate portion interposed between the cover end wall portion and the cover outer wall portion, an inner peripheral side inlet portion having an inlet hole is formed in the cover end wall portion, an outer peripheral side inlet portion having an inlet hole (635, 636) is formed in the cover intermediate portion, and the outer peripheral side inlet portion has a radial direction covering portion existing in a position nearer the frame in the axial line direction than the cover end wall portion, and an axial direction covering portion that connects the radial direction covering portion and an outer peripheral portion of the cover end wall portion, one portion of circumferential ribs configuring an inlet port of the axial direction covering portion is positioned farther to the outer side in the axial line direction than a gap between the circuit board and the first rectifying unit, and one portion of circumferential ribs configuring an inlet port of the radial direction covering portion is positioned farther to the outer side in the axial line direction than a gap between the circuit board and the second rectifying unit, wherein a cross section of the one portion of circumferential ribs configuring the inlet port of the radial direction covering portion and a cross section of the one portion of circumferential ribs configuring the inlet port of the axial direction covering portion are of a rectangular form having a plane parallel to the radial direction of the rotating shaft.