A cutting insert according to one embodiment includes upper and lower surfaces, a side surface including a front side surface, a rear side surface, and a pair of horizontal side surfaces, a first cutting edge, a second cutting edge, and a through hole extending from the upper surface to the lower surface. An opening of the through hole on a side of the upper surface is provided closer to a ridge line where the upper surface and the front side surface intersect each other than a ridge line where the upper surface and the rear side surface intersect each other. An opening of the through hole on a side of the lower surface is provided closer to a ridge line where the lower surface and the rear side surface intersect each other than a ridge line where the lower surface and the front side surface intersect each other.