A rotating electrical machine comprising: - a rotor; and - a stator disposed around an outer circumference of the rotor, wherein the rotor includes: - a plurality of coil slots formed in an axial direction on an outer circumferential surface of the rotor, the coil slots spaced from each other in a circumferential direction of the rotor; - a sub slot formed at a bottom portion of each coil slot, the sub slot opening in the axial direction of the rotor; - a winding conductor formed to be accommodated above each sub slot in each coil slot; and - a wedge formed to fix each winding conductor in the coil slot, the wedge having a hole formed in a radial direction of the rotor, - wherein each winding conductor has ventilation passages formed in two lines arranged in a width direction of the winding conductor, with a long side of each ventilation passage directed in a longitudinal direction of the winding conductor, the ventilation passages penetrating the winding conductor in the radial direction of the rotor so as to allow cooling gas to flow from the sub slot toward the wedge, - wherein sets of the two lines of ventilation passages are formed in the same shape at a plurality of positions spaced from each other in the longitudinal direction of each winding conductor, characterised in that the following expression is satisfied, 0.3 ≦ W 2 / W 1 ≦ 0.7 where W1 is a width dimension of each ventilation passage in the longitudinal direction of each winding conductor, and W2 is a width dimension from one end of each ventilation passage to one end, on the same side, of another ventilation passage adjacent thereto in the longitudinal direction of the winding conductor, and wherein the following expression is satisfied, 0.025 ≦ W 4 / W 3 ≦ 0.08 where W3 is a width dimension of each winding conductor and W4 is a width dimension of each single ventilation passage. - a rotor; and - a stator disposed around an outer circumference of the rotor, wherein the rotor includes: - a plurality of coil slots formed in an axial direction on an outer circumferential surface of the rotor, the coil slots spaced from each other in a circumferential direction of the rotor; - a sub slot formed at a bottom portion of each coil slot, the sub slot opening in the axial direction of the rotor; - a winding conductor formed to be accommodated above each sub slot in each coil slot; and - a wedge formed to fix each winding conductor in the coil slot, the wedge having a hole formed in a radial direction of the rotor, - a plurality of coil slots formed in an axial direction on an outer circumferential surface of the rotor, the coil slots spaced from each other in a circumferential direction of the rotor; - a sub slot formed at a bottom portion of each coil slot, the sub slot opening in the axial direction of the rotor; - a winding conductor formed to be accommodated above each sub slot in each coil slot; and - a wedge formed to fix each winding conductor in the coil slot, the wedge having a hole formed in a radial direction of the rotor, - wherein each winding conductor has ventilation passages formed in two lines arranged in a width direction of the winding conductor, with a long side of each ventilation passage directed in a longitudinal direction of the winding conductor, the ventilation passages penetrating the winding conductor in the radial direction of the rotor so as to allow cooling gas to flow from the sub slot toward the wedge, - wherein sets of the two lines of ventilation passages are formed in the same shape at a plurality of positions spaced from each other in the longitudinal direction of each winding conductor, characterised in that