An illuminance detecting component includes: a supporting substrate including a substrate body made of silicon, and pads provided on an upper surface of the substrate body; a plurality of light receiving elements connected electrically to the pads and receiving light irradiated from an outside, the plurality of light receiving elements being arranged in array fashion on the upper surface side; external connection terminals connected electrically to the light receiving elements; and a translucent member provided on the substrate body. In the illuminance detecting component, an airtight space in which the plurality of light receiving elements are accommodated is formed between the translucent member and the substrate body.