Two types of polymerization of hydroxy-containing diazoacetates are described. The polymerization of hydroxy-containing diazoacetates using palladium complexes proceeded successfully under chain-growth mechanism even without a protecting group to give C-C main chain polymers bearing a hydroxy-containing ester substituent on each carbon of the backbone. The resulting polymers had a slightly branched structure due to chain transfer reaction with the hydroxy groups, while the polymers obtained by polymerization of silyl-protected diazoacetates and subsequent deprotection had a completely linear structure. The hydroxy-containing polymers with an appropriate hydrophilic/hydrophobic balance showed a lower critical solution temperature-type phase separation in an aqueous medium. On the other hand, the polymerization of hydroxy-containing diazoacetates using InCl3 as a catalyst proceeded under step-growth mechanism to give oligomers having a distinct repeating unit (ester-ether), where a new ether bond was generated through O-H insertion reaction of diazocarbonyl groups into hydroxy groups.