A force sensor includes a force receiver which receives a force or a moment that acts on a detection target part, and a strain element which is provided to a sensor base and which serves as an elastic support that supports the force receiver. The force sensor includes two systems of detecting sections which each independently detect strain of four beam parts of the strain element, two systems of computing circuits which each independently compute, on the basis of a detection result that has been outputted from a corresponding one of the two systems of detecting sections, the force or the moment that acts on the detection target part, and two systems of output sections which each independently output, as an electrical signal, a computation result that has been outputted from a corresponding one of the two systems of computing circuits.