In a fluorescence detection device and a fluorescence detection method, forward-scattered light which is scattered from a measurement object irradiated with a laser beam is received and detection signals for informing the measurement object passing through the measurement point and for identifying a focus position of the forward-scattered light are produced. While, fluorescence emitted by the measurement object is received through a collecting lens and a light-reception signal of the fluorescence is outputted. The fluorescence intensity level is outputted based on the outputted light-reception signal and the produced detection signals. A focus position of the forward-scattered light is identified from the produced detection signals and the light reception-signal is corrected using a correction coefficient corresponding to the identified focus position.