In a force sensor according to one embodiment, a main body is cylindrical. A cylindrical movable body is movable with respect to the main body and includes at least three circular openings in the outer circumference thereof. A strain body is fixed to the main body and the movable body and is deformable according to the movement of the movable body. Strain sensors are provided on the strain body. A first stopper is arranged inside each of the openings and includes a first outer circumferential surface including a first outer diameter less than a diameter of the opening. Sealing members are configured to cover at least the openings and a movable part between the main body and the movable body.