we present a calculation of the K --> pipi decay amplitudes from the K --> pi matrix elements using leading order relations derived in chiral perturbation theory. Numerical simulations are carried out in quenched QCD with the domain-wall fermion action and the renormalization group improved gluon action. Our results show that the I = 2 amplitude is reasonably consistent with experiment whereas the I = 0 amplitude is sizably smaller. Consequently the DeltaI = 1/2 enhancement is only half of the experimental value, and epsilon'/epsilon is negative.