Porphyrin compounds consisting of porphyrin rings fused in a single direction by three bonds, i.e.,

A porphyrin ring-fusion polymer which consists of two or more Zn(II)-porphyrin rings fused in a single direction and in which any two porphyrin rings adjacent to each other are fused by three covalent bonds, that is, one meso-meso carbon bond (i.e., one bond between meso-position carbon atoms) and two β—β carbon bonds (i.e., two bonds between β-position carbon atoms adjacent to the meso-position carbon atoms); a process for preparing the porphyrin ring-fusion polymer regioselectively by conducing the fusion reaction in an aromatic hydrocarbon solvent in the presence of a quinoline and Lewis acid containing rare earth element under reflux; and fused-ring porphyrin compound obtained by subjecting the porphyrin ring-fusion polymer to demetallization or replacement of the Zn atoms by other metal atoms.