Abstract: Sunlight passes through the light-transmission sections of a periodic pattern reticle of a sun sensor, and light components thus divided at regular intervals are incident on the light-receiving surface of a photoelectric converting section. The photoelectric converting section transfers charges stored in the light-receiving sections, in response to a pulse signal from a transfer pulse-generating section, to convert the light intensity distribution to a time series signal. A reference phase signal-generating section generates a reference phase signal whose polarity is inverted at an interval corresponding to the width and interval of the light-transmission sections, based on the pulse signal from the transfer pulse generator. An error voltage-detecting section multiplies the reference phase signal by the time series signal, and integrates the result of multiplication to detect an error voltage corresponding to the phase difference between the two signals.