This encoder comprises: an encoder main circuit that is driven using an encoder main circuit driving voltage supplied from at least one internal power source to generate rotation information of a rotating element; an overvoltage breakdown prevention circuit that generates an abnormality detection unit driving voltage on the basis of a voltage supplied from a main power source; an abnormality detection unit that is driven using the abnormality detection unit driving voltage outputted from the overvoltage breakdown prevention circuit to detect an abnormality related to the internal power source; and a cut-off circuit that cuts off supply of the encoder main circuit driving voltage from the internal power source to the encoder main circuit upon detection by the abnormality detection unit of an abnormality.