A cover film having at least (A) a substrate layer, (B) an intermediate layer, (C) an adhesive layer, and (D) a heat seal layer having a heat sealable resin, a thermoplastic resin of the (D) heat sealing layer having a mixture of two types of (meth)acrylic acid ester copolymers having different glass transition temperatures and a hydrazide compound, wherein one of the (meth)acrylic acid ester copolymer in the (meth)acrylic acid ester copolymer mixture has a glass transition temperature of −20 to 10° C. and the other (meth)acrylic acid ester copolymer has a glass transition temperature of 40 to 80° C.