A marine vessel comprising: a ship; a pair of flaps; and a wedge provided at an end portion of a ship bottom on a stern side between the pair of flaps in a ship width direction, the ship including: the ship bottom, a stern end face rising from an end portion of the ship bottom on the stern side, and a stern opening formed in the stern end face, the pair of flaps being provided, at the stern end face, separated from each other in the ship width direction while avoiding the stern opening, wherein positions in the ship width direction of end portions of the wedge on outer sides in the ship width direction overlap with positions in the ship width direction of an end portion of the respective flaps on an inner side in the ship width direction, and the wedge includes a lower wedge surface smoothly connected to the ship bottom, wherein the lower wedge surface includes a first lower surface and a pair of second lower surfaces, the first lower surface is formed in a planar shape extending from the ship bottom to the stern side so as to be positioned downward toward the stern side in a side view, wherein the pair of second lower surfaces are provided on outer sides of the first lower surface in the ship width direction, the pair of second lower surfaces smoothly connect the side end of the first lower surface on the outer side in the ship width direction and the ship bottom, and wherein the pair of second lower surfaces are formed in a triangular shape so that the dimension in the travel direction becomes smaller toward an outer side in the ship width direction in a plan view. a ship; a pair of flaps; and a wedge provided at an end portion of a ship bottom on a stern side between the pair of flaps in a ship width direction, the ship including: the ship bottom, a stern end face rising from an end portion of the ship bottom on the stern side, and a stern opening formed in the stern end face, the pair of flaps being provided, at the stern end face, separated from each other in the ship width direction while avoiding the stern opening, wherein positions in the ship width direction of end portions of the wedge on outer sides in the ship width direction overlap with positions in the ship width direction of an end portion of the respective flaps on an inner side in the ship width direction, and the wedge includes a lower wedge surface smoothly connected to the ship bottom, wherein the lower wedge surface includes a first lower surface and a pair of second lower surfaces, the first lower surface is formed in a planar shape extending from the ship bottom to the stern side so as to be positioned downward toward the stern side in a side view, wherein the pair of second lower surfaces are provided on outer sides of the first lower surface in the ship width direction, the pair of second lower surfaces smoothly connect the side end of the first lower surface on the outer side in the ship width direction and the ship bottom, and wherein the pair of second lower surfaces are formed in a triangular shape so that the dimension in the travel direction becomes smaller toward an outer side in the ship width direction in a plan view. the ship bottom, a stern end face rising from an end portion of the ship bottom on the stern side, and a stern opening formed in the stern end face, the pair of flaps being provided, at the stern end face, separated from each other in the ship width direction while avoiding the stern opening, wherein positions in the ship width direction of end portions of the wedge on outer sides in the ship width direction overlap with positions in the ship width direction of an end portion of the respective flaps on an inner side in the ship width direction, and the wedge includes a lower wedge surface smoothly connected to the ship bottom, wherein the lower wedge surface includes a first lower surface and a pair of second lower surfaces, the first lower surface is formed in a planar shape extending from the ship bottom to the stern side so as to be positioned downward toward the stern side in a side view, wherein the pair of second lower surfaces are provided on outer sides of the first lower surface in the ship width direction, the pair of second lower surfaces smoothly connect the side end of the first lower surface on the outer side in the ship width direction and the ship bottom, and wherein the pair of second lower surfaces are formed in a triangular shape so that the dimension in the travel direction becomes smaller toward an outer side in the ship width direction in a plan view.