An adhesive composition is provided which exhibits an excellent adhesion rate on metals and low-polarity thermoplastic elastomers, and is excellent in appearance with no clouding of hardened bodies and is good in storage stability. It is a 2-cyanoacrylate-based adhesive composition which includes (a) a 2-cyanoacrylic acid ester and (b) an onium salt represented by the general formula: C+A−(1) where, in formula (1), C+ represents an onium cation, and A− represents a bis(fluorosulfonyl)imide anion.