PURPOSE: To obtain a detecting device as an accurate solar sensor photoelectric system, by installing a linear slit available for transmission of light formed in the perpendicular direction relative to a semiconductor chip at the bottom surface of a window-glass located above the linear image sensor semiconductor chip.

CONSTITUTION: A CCD linear image sensor semiconductor chip 3 is installed tightly on the inside bottom surface of a box-shaped solar sensor detecting device box 5 and a window-glass 4 is installed tightly at an opening of the box located above this chip. A light transmitting slit 6 is formed on the bottom surface of the glass 4 in the direction perpendicular to the chip 3. And, when the sun is located on the X-Z plane or inclined from this plane, the sun light passing through the slit 6 passes a point C or D. By this arrangement, when the sun is located inclined from the X-Z plane also, the point A at which the chip 3 of a slit image arrives at the light-receiving surface does not change up to a distance l away from the axis X allowing accurate detection of the direction of the sun. Consequently, a detecting device can be obtained as an accurate solar sensor photoelectric system without being affected by refraction of the glass 4 and without adversely damaged by poor protection of the chip 3.