To enhance detection accuracy for an angle of incidence of the sun light about a non-sensitive axis by expanding a detection range where incidence of the sun light is detected.

The apparatus is provided with a sun sensor 1 which has a one-dimensional CCD 11 set at an inner bottom part of a housing 10, a slit 12 formed in a sun light detection face opposite to the CCD 11 to be perpendicular to a one-dimensional arrangement direction of the CCD 11, and a signal- processing circuit 13 which receives a detection signal from the CCD 11 and obtains a direction of the sun through a predetermined processing of the signal, a motor 3 for rotating and driving the sun sensor 1, and an angle detection- processing circuit 5 which receives an output from the sun sensor 1 via a slip ring 2 and calculates an angle in the direction of the sun on the basis of the signal received thereby. When the angle in the direction of the sun of the sun sensor 1 is about to go out of the present view field of the sun sensor, the motor 3 is rotated by a required angle, thereby securing a fresh view field of the sun sensor.