A sentinel lymph node detecting apparatus 1 includes: an excitation light source unit 2 that illuminates an excitation light 10 onto a living body observation portion 20 including a sentinel lymph node 21 near a tumor into which a fluorescent dye that emits fluorescence is injected; an optical filter 3 that transmits a fluorescence image 11; an image pickup device 4 that is integral with excitation light source unit 2 and picks up fluorescence image 11 transmitted through optical filter 3; an adjusting device 5 that adjusts the picked-up observation image; and an image displaying device 6 that displays the adjusted observation image. Adjusting device 5 adjusts at least one of a luminance and a contrast of the observation image. A lymph node detecting apparatus that is simple in apparatus arrangement, is easy to handle, and enables good images to be obtained is thereby realized.