To provide a photosensor with signal processing function in which processing at a post-stage signal processing circuit is simplified while widening the dynamic range, and conventional parts can be employed as they are.

The photosensor 10 delivers a signal exhibiting linear output characteristics when the illuminance of incident light is lower than a first specified level and delivers a signal exhibiting logarithmic output characteristics when the illuminance of incident light is higher than the first specified level. A characteristics converting means 12 converts the output signal from the photosensor 10 into a signal exhibiting logarithmic output characteristics corresponding to the illuminance of incident light and delivers the converted signal as a sensor signal.