A light detection device comprising: a package including a window configured to allow light to enter therefrom; a Fabry-Perot interference filter arranged in the package and configured to transmit the light incident from the window; and a light detector arranged in the package in a state of being separated from the Fabry-Perot interference filter, the light detector configured to detect the light transmitted by the Fabry-Perot interference filter, wherein the Fabry-Perot interference filter includes: a substrate having a first surface on the window side and a second surface on the light detector side; a first layer structure arranged on the first surface, the first layer structure having a first mirror and a second mirror facing each other via a gap, a distance between the first mirror and the second mirror being variable; a lens unit integrally formed on the second surface side and configured to condense the light transmitted by the first mirror and the second mirror onto the light detector; and a second layer structure arranged on the second surface and structured to correspond to the first layer structure, wherein an opening is formed in the second layer structure, the opening through which the light transmitted by the first mirror and the second mirror passes, and wherein the lens unit is attached to the second layer structure so as to close the opening. a package including a window configured to allow light to enter therefrom; a Fabry-Perot interference filter arranged in the package and configured to transmit the light incident from the window; and a light detector arranged in the package in a state of being separated from the Fabry-Perot interference filter, the light detector configured to detect the light transmitted by the Fabry-Perot interference filter, wherein the Fabry-Perot interference filter includes: a substrate having a first surface on the window side and a second surface on the light detector side; a first layer structure arranged on the first surface, the first layer structure having a first mirror and a second mirror facing each other via a gap, a distance between the first mirror and the second mirror being variable; a lens unit integrally formed on the second surface side and configured to condense the light transmitted by the first mirror and the second mirror onto the light detector; and a second layer structure arranged on the second surface and structured to correspond to the first layer structure, wherein an opening is formed in the second layer structure, the opening through which the light transmitted by the first mirror and the second mirror passes, and wherein the lens unit is attached to the second layer structure so as to close the opening. a substrate having a first surface on the window side and a second surface on the light detector side; a first layer structure arranged on the first surface, the first layer structure having a first mirror and a second mirror facing each other via a gap, a distance between the first mirror and the second mirror being variable; a lens unit integrally formed on the second surface side and configured to condense the light transmitted by the first mirror and the second mirror onto the light detector; and a second layer structure arranged on the second surface and structured to correspond to the first layer structure, wherein an opening is formed in the second layer structure, the opening through which the light transmitted by the first mirror and the second mirror passes, and wherein the lens unit is attached to the second layer structure so as to close the opening.