PURPOSE: To provide an epoxy-based adhesive composition giving excellent tackiness at normal temperatures, and also giving tough adhesiveness on curing by heating.

CONSTITUTION: The objective composition can be obtained by incorporating (A) 100 pts.wt. of a liquid epoxy resin (Epikote 828) with (B) 25 pts.wt. of a carboxyl group-contg. vinyl chloride-based polymer prepared by copolymerization between 100 pts.wt. of vinyl chloride and 6 pts.wt. of monobutyl maleate and (C) 10 pts.wt. of dicyandiamide. A polyester film 25μm thick is coated with this composition at a thickness of 50μm followed by heating at 120°C for 15min to obtain the second objective tacky film. The third objective usage of this composition is such that the surface of a base is coated with this composition followed by heating at 120°C for 15min to form a tacky film which is then laminated with another base followed by heating at 180°C for 60min to effect curing.