In the detection of fluorescence Lf emitted by a micro-object irradiated with an excitation light Le by a semiconductor light-detecting element 20, a converging microlens 62 for converging the excitation light Le elevating the optical density thereof and irradiating the micro-object with the light, causing the micro-object to generate fluorescence Lf due to two-photon absorption, is inserted partway along the light path of the excitation light Le. This enables the fluorescence Lf emitted by the micro-object to be detected with high sensitivity.