Fluorescence detection device

A fluorescence detection device comprising:

• a substrate;
• a light source configured to output excitation light to a sample;
• and
• a detector configured to detect fluorescence, wherein
• the detector comprises
• a light guide layer having a first surface and a second surface opposite to the first surface and having a light-transmitting property,
• a through-hole penetrating the light guide layer from the first surface to the second surface in a direction perpendicular to the substrate,
• a light-receiving element covered by the light guide layer and configured to receive fluorescence emitted from the sample due to the excitation light, and
• a light-reducing layer provided on the light guide layer and configured to reduce transmission of the excitation light,
• the light-reducing layer has a plurality of openings,
• a plurality of housing parts each surrounded by a sidewall of the through-hole and configured to accommodate the sample are formed,
• the openings are formed at positions overlapping the housing parts, and
• the light-receiving element is disposed surrounding each of the housing parts in plan view.