A straddled vehicle comprising: a storage box that defines a storage space in which an article is to be disposed; a seat that is disposed above the storage box in an up-down direction of the vehicle and opens and closes an opening provided in an upper end of the storage space by turning upward and downward with respect to the storage box; a frame that includes a pair of rear frames that are disposed on a right side and a left side of the storage box in a right-left direction of the vehicle, respectively, and a mount bracket that protrudes upward from one of the pair of rear frames in the up-down direction of the vehicle and supports the storage box; and an exterior cover that includes a pair of rear side covers disposed on the right side and the left side of the pair of rear frames, respectively, and a rear center cover disposed between the pair of rear side covers, wherein the rear side covers are disposed under the seat in a side view of the vehicle, wherein each of the rear side covers is disposed outward of the pair of rear frames in a vehicle width direction and overlaps the storage box and the pair of rear frames in the side view of the vehicle, wherein the storage box includes a tubular portion that surrounds the storage space, a flange portion that protrudes from an outer circumferential surface of the tubular portion and a mount portion that is disposed on the mount bracket, characterized in that the mount portion extends downward from the flange portion in the up-down direction of the vehicle, each of the rear side covers includes an upper end portion that overlaps the flange portion in a plan view of the vehicle and a notch that penetrates the upper end portion in the up-down direction of the vehicle and is recessed outward in the vehicle width direction in a plan view of the vehicle, and the mount portion is disposed inside of the notch of one of the rear side covers in a plan view of the vehicle. a storage box that defines a storage space in which an article is to be disposed; a seat that is disposed above the storage box in an up-down direction of the vehicle and opens and closes an opening provided in an upper end of the storage space by turning upward and downward with respect to the storage box; a frame that includes a pair of rear frames that are disposed on a right side and a left side of the storage box in a right-left direction of the vehicle, respectively, and a mount bracket that protrudes upward from one of the pair of rear frames in the up-down direction of the vehicle and supports the storage box; and an exterior cover that includes a pair of rear side covers disposed on the right side and the left side of the pair of rear frames, respectively, and a rear center cover disposed between the pair of rear side covers, wherein the rear side covers are disposed under the seat in a side view of the vehicle, wherein each of the rear side covers is disposed outward of the pair of rear frames in a vehicle width direction and overlaps the storage box and the pair of rear frames in the side view of the vehicle, wherein the storage box includes a tubular portion that surrounds the storage space, a flange portion that protrudes from an outer circumferential surface of the tubular portion and a mount portion that is disposed on the mount bracket, characterized in that the mount portion extends downward from the flange portion in the up-down direction of the vehicle, each of the rear side covers includes an upper end portion that overlaps the flange portion in a plan view of the vehicle and a notch that penetrates the upper end portion in the up-down direction of the vehicle and is recessed outward in the vehicle width direction in a plan view of the vehicle, and the mount portion is disposed inside of the notch of one of the rear side covers in a plan view of the vehicle.