A main wing for an aircraft having an aircraft axis direction defined as a direction of a fuselage of the aircraft, the main wing comprising: a main wing body; a flap including a flap body that is provided so as to be deployable from the main wing body, the flap body having a wing tip on an outboard side in a span direction of the flap body; and at least one of: - a protruding portion formed on a lower surface of a tip part (40INB,40OTB) of the flap body on at least the outboard side in a streamline shape such that a protrusion amount from the flap body is increased from a leading edge side toward a middle part of the protruding portion in a length direction, and such that the protrusion amount from the flap body is then decreased toward a trailing edge, and - a round part present on the lower surface of the wing tip of the flap, wherein the round part is formed by rounding a corner formed by the lower surface and an end surface of the flap body in the span direction, wherein the flap further comprises a plurality of inclined portions that each protrude from an upper surface of the tip part (40INB,40OTB) on at least the outboard side in the span direction of the flap body within a region from a position of a side end edge of the flap body to a position that is separated from the side end edge by a chord length of the flap body in the span direction, and are each inclined in the same direction with respect to the aircraft axis direction; and the inclined portions are arranged in the span direction with predetermined intervals such that a rear end of the inclined portions is located closer to the side end edge of the tip part (40INB,40OTB) in the span direction of the flap body than a virtual line that passes through a front end of the respective inclined portion and is parallel to the aircraft axis direction. a main wing body; a flap including a flap body that is provided so as to be deployable from the main wing body, the flap body having a wing tip on an outboard side in a span direction of the flap body; and at least one of: - a protruding portion formed on a lower surface of a tip part (40INB,40OTB) of the flap body on at least the outboard side in a streamline shape such that a protrusion amount from the flap body is increased from a leading edge side toward a middle part of the protruding portion in a length direction, and such that the protrusion amount from the flap body is then decreased toward a trailing edge, and - a round part present on the lower surface of the wing tip of the flap, wherein the round part is formed by rounding a corner formed by the lower surface and an end surface of the flap body in the span direction, - a protruding portion formed on a lower surface of a tip part (40INB,40OTB) of the flap body on at least the outboard side in a streamline shape such that a protrusion amount from the flap body is increased from a leading edge side toward a middle part of the protruding portion in a length direction, and such that the protrusion amount from the flap body is then decreased toward a trailing edge, and - a round part present on the lower surface of the wing tip of the flap, wherein the round part is formed by rounding a corner formed by the lower surface and an end surface of the flap body in the span direction, wherein the flap further comprises a plurality of inclined portions that each protrude from an upper surface of the tip part (40INB,40OTB) on at least the outboard side in the span direction of the flap body within a region from a position of a side end edge of the flap body to a position that is separated from the side end edge by a chord length of the flap body in the span direction, and are each inclined in the same direction with respect to the aircraft axis direction; and the inclined portions are arranged in the span direction with predetermined intervals such that a rear end of the inclined portions is located closer to the side end edge of the tip part (40INB,40OTB) in the span direction of the flap body than a virtual line that passes through a front end of the respective inclined portion and is parallel to the aircraft axis direction.