To provide a new fluorine-containing surface treatment agent composition having high substantivity of water repellency and water drop slidable property.

The surface treatment agent composition comprises a compound of formula (I) and a compound of formula (A). When the fluorine-containing surface treatment agent composition is applied to a base material such as glass, metal or plastic and dried, a treated base material having surface properties such as solvent resistance, chemical resistance, water repellency, water sliding property and releasability and high substantivity of these effects can be obtained.