In a position detector for detecting a position of a detection body, a signal processing circuit processes a signal outputted from a magnetic field detection element. A first storage circuit stores the signal outputted from the magnetic field detection element and outputs a signal to an external device through an output circuit in a normal operation mode. A second storage circuit stores an output value of the first storage circuit. When a malfunction determination circuit determines an instantaneous power interruption mode, a signal route changing circuit prevents a signal transmission between the first storage circuit and the second storage circuit and a signal transmission between the first storage circuit and the output circuit, prevents the second storage circuit from updating data for a certain period of time, and permits the second storage circuit in which updating is prevented to output a signal to the output circuit.