The invention has for its object to provide a water-soluble phthalocyanine dye unlikely to lose its own properties even upon dissolved in a concentration as high as 10−5 M.The inventive water-soluble phthalocyanine dye is characterized by having a sulfuric acid group or groups as an axial ligand or ligands of an antimony/phthalocyanine complex. The sulfuric acid group or groups have been introduced by replacing a part or the whole of hydroxyl groups in the starting material with a sulfuric acid group or groups.