A rotational body comprising: a rotational shaft; an impeller mating with the rotational shaft on an end side of the rotational shaft; and a nut screwed on the rotational shaft on an end side of the rotational shaft to fasten the rotational shaft and the impeller together, wherein the impeller includes a hub portion having a peripheral surface inclined to an axial direction of the rotational shaft and having an insert hole in which the rotational shaft is inserted, and a blade portion provided so as to protrude from the circumferential surface of the hub portion toward a radial direction, wherein at least one of the rotational shaft or the insert hole of the hub portion has formed an interference fit portion (2A, 10) for fit between the impeller and the rotational shaft where an outside diameter of the rotational shaft is larger than an inside diameter of the insert hole of the hub portion, and wherein the interference fit portion (2A, 10) is, in the axial direction of the rotational shaft, in a region which does not include a largest outside diameter portion where the hub portion has a largest outside diameter, with the rotational shaft and the impeller mating with each other, wherein the interference fit portion (2A,10) is apart from the nut in the axial direction of the rotational shaft, with the rotational shaft and the impeller mating with each other, and wherein the interference fit portion is, in the axial direction of the rotational shaft, in a region which includes an axial middle position of the hub portion, with the rotational shaft and the impeller mating with each other, characterized in that the interference fit portion (2A, 10) includes a larger-diameter portion of the rotational shaft, the larger-diameter portion having a larger diameter than the rest of the rotational shaft. a rotational shaft; an impeller mating with the rotational shaft on an end side of the rotational shaft; and a nut screwed on the rotational shaft on an end side of the rotational shaft to fasten the rotational shaft and the impeller together, wherein the impeller includes a hub portion having a peripheral surface inclined to an axial direction of the rotational shaft and having an insert hole in which the rotational shaft is inserted, and a blade portion provided so as to protrude from the circumferential surface of the hub portion toward a radial direction, wherein at least one of the rotational shaft or the insert hole of the hub portion has formed an interference fit portion (2A, 10) for fit between the impeller and the rotational shaft where an outside diameter of the rotational shaft is larger than an inside diameter of the insert hole of the hub portion, and wherein the interference fit portion (2A, 10) is, in the axial direction of the rotational shaft, in a region which does not include a largest outside diameter portion where the hub portion has a largest outside diameter, with the rotational shaft and the impeller mating with each other, wherein the interference fit portion (2A,10) is apart from the nut in the axial direction of the rotational shaft, with the rotational shaft and the impeller mating with each other, and wherein the interference fit portion is, in the axial direction of the rotational shaft, in a region which includes an axial middle position of the hub portion, with the rotational shaft and the impeller mating with each other, characterized in that the interference fit portion (2A, 10) includes a larger-diameter portion of the rotational shaft, the larger-diameter portion having a larger diameter than the rest of the rotational shaft.