Abstract: In a double row rolling bearing for supporting a pinion shaft, an outer ring is fixed to an inner peripheral surface of an annular wall (case) with its axis disposed horizontally, and an inner ring assembly is fitted on a pinion shaft, and is inserted, together with the pinion shaft, horizontally into the outer ring through a larger-diameter opening of the outer ring, and is mounted in the outer ring. A larger-diameter cage has a drop limitation portion for limiting the vertically-downward movement of the larger-diameter case.