A rotor blade (23, 55) used for any one of a fan and a compressor of an aircraft engine, and using a composite material of fibers and a matrix resin as a constituent material, the rotor blade comprising: a rotor blade main body; and a rotor blade root portion formed integrally on a base end side of the rotor blade main body; wherein the rotor blade main body is formed by stacking a plurality of composite sheets each made from the fibers and the matrix resin, and includes a plurality of first composite sheet groups and a plurality of second composite sheet groups which are provided in a blade thickness direction; each first composite sheet group includes a plurality of the composite sheets (49A, 49B, 49C) which are stacked one on another from a blade thickness center side toward a dorsal surface, and which are different from one another in terms of an orientation angle of the fibers; each second composite sheet group includes a plurality of the composite sheets (49A, 49B, 49C) which are stacked one on another from the blade thickness center side toward a ventral surface, and which are different from one another in terms of the orientation angle of the fibers; and a stacking pattern of the plurality of composite sheets in the first composite sheet group and a stacking pattern of the plurality of composite sheets in the second composite sheet group are the same; characterised in that: a composite direction of orientation directions (S1, S2, S3, S4) of the fibers in the plurality of composite sheets in each of the first composite sheet group and the second composite sheet group inclines to a trailing edge from a span direction, wherein the composite direction in each of the first composite sheet group and the second composite sheet group inclines to the trailing edge by 20 degrees to 45 degrees from the span direction. a rotor blade main body; and a rotor blade root portion formed integrally on a base end side of the rotor blade main body; wherein the rotor blade main body is formed by stacking a plurality of composite sheets each made from the fibers and the matrix resin, and includes a plurality of first composite sheet groups and a plurality of second composite sheet groups which are provided in a blade thickness direction; each first composite sheet group includes a plurality of the composite sheets (49A, 49B, 49C) which are stacked one on another from a blade thickness center side toward a dorsal surface, and which are different from one another in terms of an orientation angle of the fibers; each second composite sheet group includes a plurality of the composite sheets (49A, 49B, 49C) which are stacked one on another from the blade thickness center side toward a ventral surface, and which are different from one another in terms of the orientation angle of the fibers; and a stacking pattern of the plurality of composite sheets in the first composite sheet group and a stacking pattern of the plurality of composite sheets in the second composite sheet group are the same; characterised in that: a composite direction of orientation directions (S1, S2, S3, S4) of the fibers in the plurality of composite sheets in each of the first composite sheet group and the second composite sheet group inclines to a trailing edge from a span direction, wherein the composite direction in each of the first composite sheet group and the second composite sheet group inclines to the trailing edge by 20 degrees to 45 degrees from the span direction. a composite direction of orientation directions (S1, S2, S3, S4) of the fibers in the plurality of composite sheets in each of the first composite sheet group and the second composite sheet group inclines to a trailing edge from a span direction, wherein the composite direction in each of the first composite sheet group and the second composite sheet group inclines to the trailing edge by 20 degrees to 45 degrees from the span direction.