  We study the escape of cosmic-ray (CR) protons accelerated at a supernova
remnant (SNR) by numerically solving a diffusion-convection equation from the
vicinity of the shock front to the region far away from the front. We consider
the amplifications of Alfven waves generated by the escaping CR particles and
their effects on CR escape into interstellar medium (ISM). We find that the
amplification of the waves significantly delays the escape of the particles
even far away from the shock front (on a scale of the SNR). This means that the
energy spectrum of CR particles measured through gamma-ray observations at
molecular clouds around SNRs is seriously affected by the particle scattering
by the waves.
