An .alpha.-cyanoacrylate adhesive composition including as the main components thereof:(A) an .alpha.-cyanoacrylate prepared by the process having the steps of thermally depolymerizing a condensation product obtained from a cyanoacetic acid ester, and formaldehyde or a polymer thereof using as a catalyst a polymerizable imine represented by the formula ##STR1## wherein R.sub.1 and R.sub.2 are the same or different and are each CH.sub.3 or H to obtain a crude monomer, and rectifying the crude monomer,(B) a fine particulate silica having an absorbed and adsorbed water content of 0.08 to 1.30 wt % and 2.7 to 5.2 silanol groups/100 .ANG..sup.2 on the surface thereof, and(C) an acid-treated (poly)-alkylene glycol.