  Mixed dark matter scenario can reconcile the COBE data and the observed large
scale structure. So far the massive neutrino with a mass of a few eV has been
the only discussed candidate for the hot dark matter component. We point out
that the hadronic axion in the so-called hadronic axion window, f_a \sim 10^6
GeV, is a perfect candidate as hot dark matter within the mixed dark matter
scenario. The current limits on the hadronic axion are summarized. The most
promising methods to verify the hadronic axion in this window are the resonant
absorption of almost-monochromatic solar axions from M1 transition of the
thermally excited $^{57}$Fe in the Sun, and the observation of the ``axion
burst'' in water \v{C}erenkov detectors from another supernova.
