There is provided an ICG-loaded polymer nanoparticle that is dynamically stable, prevents the leakage of contained ICG and the resulting discoloration, and has a high molar absorbance coefficient. The particle contains a hydrophilic dye having a sulfonate group and a hydrophobic polymer, and the particle further contains at least one of a lipid having a positively charged region, a nicotinic acid derivative and a thiamine derivative.
