  We study glueballs in the holographic gauge theories, supersymmetric and
non-super symmetric cases, which are given by the type IIB superstring
solutions with non-trivial dilaton. In both cases, the dilaton reflects the
condensate of the gauge field strength, $<F^2>$, which is responsible to the
linear confining potential between the quark and anti-quark. Then we could see
the meson spectra. On the other hand, the glueball spectra are not found in the
supersymmetric case. We need a sharp wall, which corresponds to an infrared
cutoff, in order to obtain the glueballs. In the non-supersymmetric case, the
quantized glueballs are actually observed due to the existence of such a wall
driven by the dilaton. The strings and D-branes introduced as building blocks
of hadrons are pushed out by this wall, and we could see the Regge behavior of
the higher spin meson and glueball states. We find that the slope of the
glueball trajectory is half of the flavor meson's one. As for the low spin
glueballs, they are studied by solving the fluctuations of the bulk fields, and
their discrete spectra are shown.
