A spectral sensor includes a wiring substrate which has a principal surface; a light detector which is disposed on the principal surface of the wiring substrate and is electrically connected to the wiring substrate; spacer which is disposed around the light detector, on the principal surface of the wiring substrate; and a Fabry-Perot interference filter which has a light transmission region and is disposed on the principal surface of the wiring substrate with the spacer therebetween. The spacer support the Fabry-Perot interference filter in a surrounding region of the light transmission region and the spacer is arranged to form opening communicating with an inner side of the surrounding region and an outer side of the surrounding region, when viewed from a light transmission direction in the light transmission region.