Disclosed is a near-infrared fluorescent imaging agent comprising an indocyanine-based fluorescent dye and a liposome. The near-infrared fluorescent imaging agent of the present invention demonstrates high fluorescence intensity and a long anchoring time in sentinel lymph nodes, thereby making it useful for detecting sentinel lymph nodes in sentinel lymph node navigation surgery. Also disclosed is an indocyanine green derivative that is particularly suitable for use in the near-infrared fluorescent imaging agent of the present invention.
