A lymph node detecting apparatus comprising: a light source unit including a plurality of excitation light sources and a plurality of illumination light sources, each of the plurality of excitation light sources illuminating an excitation light onto a biological observation location that includes a lymph node near a tumor into which a fluorescent dye that emits a fluorescence of a predetermined wavelength has been injected in advance and each of the plurality of illumination light sources illuminating the biological observation location with an illumination light of a wavelength set so as to be included in the transmission wavelength band; an optical filter, transmitting light in a transmission wavelength band that includes the wavelength of the fluorescence emitted from the biological observation location upon illumination of the excitation light; an image pickup means, picking up a fluorescence image and a normal image, the fluorescence image resulting from the fluorescence emitted from the biological observation location and transmitted through the optical filter, the normal image resulting from reflected light due to reflection of the illumination light by the biological observation location and transmitted through the optical filter, the image pickup means outputting a respectively corresponding fluorescence observation image and normal observation image; an image display means, displaying the fluorescence observation image and the normal observation image, output from the image pickup means, as images for detecting the lymph node; and a supporting member having a first principal surface, supporting the excitation light sources and the illumination light sources integrally, and a surface defining an opening portion that passes through in a direction intersecting the first principal surface, and wherein a central axis of the supporting member matches an optical axis (Ax) of said light source unit, and said optical axis of the light source unit matches an optical axis of the image pickup means, the supporting member has the opening portion is at a central portion that includes an axis (Ax), which is said optical axis (Ax) and the central axis of the supporting member, the opening portion is formed as a penetrating hole along the axis (Ax), and the excitation light sources and the illumination light sources are arrayed in two dimensions so as to surround the opening portion on the first principal surface. a light source unit including a plurality of excitation light sources and a plurality of illumination light sources, each of the plurality of excitation light sources illuminating an excitation light onto a biological observation location that includes a lymph node near a tumor into which a fluorescent dye that emits a fluorescence of a predetermined wavelength has been injected in advance and each of the plurality of illumination light sources illuminating the biological observation location with an illumination light of a wavelength set so as to be included in the transmission wavelength band; an optical filter, transmitting light in a transmission wavelength band that includes the wavelength of the fluorescence emitted from the biological observation location upon illumination of the excitation light; an image pickup means, picking up a fluorescence image and a normal image, the fluorescence image resulting from the fluorescence emitted from the biological observation location and transmitted through the optical filter, the normal image resulting from reflected light due to reflection of the illumination light by the biological observation location and transmitted through the optical filter, the image pickup means outputting a respectively corresponding fluorescence observation image and normal observation image; an image display means, displaying the fluorescence observation image and the normal observation image, output from the image pickup means, as images for detecting the lymph node; and a supporting member having a first principal surface, supporting the excitation light sources and the illumination light sources integrally, and a surface defining an opening portion that passes through in a direction intersecting the first principal surface, and wherein a central axis of the supporting member matches an optical axis (Ax) of said light source unit, and said optical axis of the light source unit matches an optical axis of the image pickup means, the supporting member has the opening portion is at a central portion that includes an axis (Ax), which is said optical axis (Ax) and the central axis of the supporting member, the opening portion is formed as a penetrating hole along the axis (Ax), and the excitation light sources and the illumination light sources are arrayed in two dimensions so as to surround the opening portion on the first principal surface.