In a self-aligning bearing positioning and supporting one end of a rotation shaft in an axial direction and allowing the rotation shaft to bend, the bearing is structured as a double row cylindrical roller bearing with aligning ring, a first row of cylindrical roller group is positioned by being held in an axial direction between a radially inward flange provided in an intermediate portion in an axial direction of an outer ring having an outer peripheral surface formed in a spherical surface shape, and a flange provided in one outer end of two inner rings, and a second row of cylindrical roller group is positioned by being held in the axial direction between the flange of the outer ring and a flange provided in another outer ends of the two inner rings.