  We examine the collapse of an axion domain wall bounded by an axionic string.
It is found that the collapse proceeds quickly and axion domain walls
disappear. However axions are emitted in the collapse and its energy density
increases during radiation dominated era and contributes significantly to the
present mass density of the universe. In particular the axion emitted from the
wall can account for the dark matter in the universe for $F_a\gsim
10^{10}\GeV$.
