According to one embodiment, a light detector includes a conductive layer, a first element, a second element, a first member, a first insulating part, and a second insulating part. The conductive layer includes a first conductive portion and a second conductive portion. The first element includes a first semiconductor layer and a second semiconductor layer. The second element includes a fourth semiconductor layer and a fifth semiconductor layer. The first member is provided between the first element and the second element and electrically connected to the conductive layer. The first member is conductive. The first insulating part is provided between the first element and the first member. The second insulating part is provided between the second element and the first member.