A covalently linked linear porphyrin polymer represented by formula (1):
##STR00001## ##STR00002## wherein R represents an alkyl group or
##STR00003## (wherein a, b and d independently represent H, an alkyl
group or aryl group); X represents --O--, --S--, >NR.sub.101 (wherein
R.sub.101 represents H or an alkyl group), --CH.sub.2-- or a single bond;
Y represents .dbd.O, .dbd.S, or 2H; m represents an integer of 0 to 4; n
represents an integer of 0 to 6; Z represents a five- or six-membered,
nitrogen-containing, coordinating hetero aromatic ring group; M
represents an ion of metal selected from typical metals and transition
metals; Q.sub.1 represents a single bond or a linear, divalent linking
group; and p.sub.1 represents an integer of 2 or more.
