The present invention provides a porphyrin derivative having improved water solubility, desirably having both water solubility and lipophilicity. Specifically, the present invention provides a water-soluble porphyrin consisting of a tetraphenylporphyrin derivative represented by Formula (1):wherein m represents an integer of 1 to 30 n represents an integer of 2 to 4 R represents a hydrogen atom or an optionally substituted alkyl or aromatic group Ph represents an optionally substituted phenyl group and X− is a counterion and represents a halide ion, PF6−, or BF4−.
