To provide a surface treatment composition which stably retains its initial hue and is excellent in abrasion resistance and a weatherstrip prepared by using the same.

This surface treatment composition is prepared by compounding a composite comprising a halogenated natural rubber and a halogenated ethylene-propylene-ethylidenenorbornene terpolymer with a hexamethylene diisocyanate-based isoyanate. When a silicone rubber is compounded into the composition, luster is arbitrarily imparted to the composition without detriment to its resistances to weather and scratch. When a polyethylene wax or polycarbonate is compounded into the composition, the luster of the composition can be arbitrarily reduced without detriment to the resistances to weather and scratch.