The present invention provides a thiophene-containing compound represented by Formula (I) and a thiophene-containing compound polymer using the thiophene-containing compound. In Formula (I), Ar1 represents a substituted or unsubstituted monovalent aromatic group; X represents a divalent straight-chain hydrocarbon group having 1 to 6 carbon atoms, a divalent branched-chain hydrocarbon group having 2 to 10 carbon atoms, or a substituted or unsubstituted divalent aromatic group; R1 to R5 each independently represent a hydrogen atom, an alkyl group, a cyano group, a halogen group, a substituted amino group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group; 1 represents an integer from 1 to 5; and m and k each independently represent 0 or 1.