Abstract: A hollow portion is provided on the core of an inner shaft (2) to form an oil feed port (3), a plurality of oil feed holes (4) which are connected with both of the outer peripheral face of the inner shaft (2) within a range (L) of the bearing surface of the inner shaft (2) and the oil feed port (3) are radially provided in a line , and axial oil grooves (5) each of which includes an inner shaft surface side opening portion (4a) of the oil feed hole (4) are provided on the outer peripheral face of the inner shaft to form a contra-rotating bearing device for a contra-rotating propeller which causes the inner shaft (2) and an outer shaft (2) to contra-rotate mutually. In place of the oil grooves, a plurality of concave-convex portions may be formed in the axial direction of a contra-rotating bearing on the inner peripheral face of the bearing and circular portions may be provided on both axial ends of the concavo-convex portions to form the contra-rotating bearing device for a contra-rotating propeller.