The pH-responsive poly(vinyl alcohol)/poly(acrylic acid) hydrogel was prepared as a drug-delivery carrier. The drug release rate from hydrogels was controlled by surface modification with oxyfluorination. The oxyfluorination in higher oxygen content produced more hydrophilic hydrogel surface area. In contrast, the fluorination with fluorine gas produced more hydrophobic hydrogel surface area. C-O bonds and C-F bonds were mainly formed by oxyfluorination and fluorination, respectively. Both the swelling ratio and the drug release rate were strongly dependent on the oxyfluorination conditions. The drug release was accelerated by oxyfluorination in higher oxygen content because the favorable affinity at the interface caused the higher swelling ratio; whereas, the sustained drug release was obtained by fluorination because of the lower swelling ratio of the hydrophobically modified hydrogels.