A near infrared fluorescent contrast agent which is excellent in permeability in a living tissue and enables specific imaging of tumor and/or blood vessel, comprising a compound represented by formula (I) or a pharmaceutically acceptable salt thereof, wherein R.sup.1, R.sup.2, R.sup.7, and R.sup.8 represent a C.sub.1-C.sub.10 alkyl group or the like; R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.9, R.sup.10, R.sup.11, and R.sup.12 represent a hydrogen atom, a C.sub.1-C.sub.6 alkyl group, an aryl group or the like; X.sup.1 and X.sup.2 represent a C.sub.1-C.sub.15 alkyl group or an aryl group and X.sup.1 and X.sup.2 in total have 0 to 4 carboxyl groups; m.sup.1, m.sup.2, and m.sup.3 represents 0 or 1; L.sup.1 to L.sup.7 independently represent a methine group; M represents a hydrogen atom, a metal, or a quaternary ammonium salt; and n represents an integer of 1 to 7 necessary for neutralizing charge.