A light detecting device includes a well region, a first holding region disposed in a surface portion of the well region, a second holding region and a third holding region disposed in a surface portion of the first holding region, an insulating layer disposed on the second holding region and the third holding region, a first electrode disposed on the second holding region through the insulating layer, and the second electrode disposed on the third holding region through the insulating layer. The first holding region is configured to hold a first carrier generated in the well region. Each of the second holding region and the third holding region is configured to hold a second carrier generated in the well region. The first carrier is one of an electron and a hole, and the second carrier is the other one of the electron and the hole.