It is a main object of the present invention to provide a wettability variable substrate provided with a wettability variable layer which is free from any cloud and is superior in adhesion to a substrate, transparency and liquid repellency. The above object is attained by the provision of a wettability variable substrate comprising a wettability variable layer, on a substrate, which the wettability is varied by exposing to light in the presence of a photocatalyst, wherein the wettability variable layer contains an organopolysiloxane which is a co-hydrolysis condensation polymer obtained using (A) one type or two or more types of organopolysiloxane precursors represented by YnSiX(4-n) (Y represents an alkyl group or a fluoroalkyl group, or a substituent containing these groups, X represents an alkoxyl group, an acetyl group or a halogen, a letter n subscripted to Y and a letter n in (4-n) subscripted to X are an integer from 1 to 3), and (B) an amorphous silica precursor represented by SiX4 (X is the same as above) by a mass ratio of (A)/(B)=1/0.1 to 1/20.