A sensing device that detects whether an edge is present or absent achieves improved accuracy in detection of an edge.
The sensing device includes a level control circuit, a comparison circuit, and an edge determination circuit. In this sensing device, the level control circuit amplifies or attenuates the signal level of one of a pair of pixel signals by a predetermined gain. The comparison circuit compares the pair of pixel signals with the signal level of the one pixel signal amplified or attenuated with each other, and outputs a result of the comparison. The edge determination circuit determines whether an edge is present or absent in reference to the comparison result.