The task of the invention provides an active energy ray-curable adhesive composition, a polarization plate, an optical film and an image display device. The adhesive composition helps to improve adhesiveness of a polarizer and a transparent protection layer and to form an adhering layer with improved heat resistance and water resistance. The method of realization is the active energy ray-curable adhesive composition comprising following components: a (A) composition which is a vinyl lactam represented by a general formula (1) and a (B) composition which is a compound with 1 molecule comprising more than two ethylenically unsaturated groups and less than 1000 in molecular weight. In a formula (1), R1 and R2 are univalent saturated hydrocarbon radicals with number of hydrogen atoms or carbon atoms being 1 to 6. R1 and R2 can be identical and different as well and can be connected together to form an annular structure.