A fluorescence detection device includes: a light source that emits excitation light in a first direction; a base unit (30) to which the light source is attached; an opening (30a) that is provided on a side in the first direction of the base unit (30) with respect to the light source; a cantilever (31) that is cantilevered to the base unit (30) to extend from an inner edge of the opening (30a) toward a center side of the opening (30a); an optical path conversion unit (20) that is fixed to a free end of the cantilever (31), converts a traveling direction of the excitation light emitted from the light source into a second direction different from the first direction, and irradiates a measurement object with the excitation light turned in the second direction; and a photodetection element that is disposed on a side of the opening (30a) opposite to the measurement object and detects fluorescence passing through the opening (30a) in fluorescence emitted from the measurement object irradiated with the excitation light. Accordingly, a loss in the fluorescence guided to the photodetection element can be reduced, and thus fluorescence detection efficiency can be improved.