To provide a small-sized, light-weight and inexpensive illuminance detector, capable of detecting the illuminance of incident light from different directions.

This illuminance detector 100 is equipped with a shielding plate 20 having a hole h1, and sensor elements s1, s2 for detecting the illuminance of light. In the illuminance detector 100, the plurality of sensor elements s1, s2 are formed on a surface layer part of the same semiconductor substrate 10, and the shielding plate 20 is arranged above the semiconductor substrate 10 where the sensor elements s1, s2 are formed; and the incident light from the outside passes through the hole h1, and the semiconductor substrate 10 is irradiated therewith, and the illuminance of the incident light from the different direction is detected respectively by the plurality of sensor elements s1, s2.