A light marker adapted to be indwelt in the vicinity of a lesion inside an organ of an object, the light marker emitting light to be picked up at an outside of the organ to allow a location of the lesion to be identified based on a position of the light on a resultant pickup image, wherein the light marker comprises liquid composed of viscous substance mixed with fluorescent substance (214) and adapted to be injected to a site underneath a mucous membrane (302) of the lesion (100). A method of identifying a location of interest on an inside wall of a tubular object to be examined, the tubular object having a wall permitting light to be transmitted therethrough using the light marker.
