It was attempted to switch the wettability of a glass surface by modification with the thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). To strengthen the PNIPAAm layer, the polymer was fixed in a silica gel matrix by a sol-gel method and coated on a glass plate. The wettability of the silica-PNIPAAm composite layer was evaluated by contact angle measurements. The effect of silica on the wettability was investigated by altering the PNIPAAm/silica molar ratio. The effect of surface roughness on the contact angle was also evaluated using atomic force microscopy (AFM). The wettability of the surface drastically dropped by elevating the temperature from 305 K to 313 K through the lower critical solution temperature (LCST) of PNIPAAm.