  We investigate future constraints on primordial local-type non-Gaussianity
from 21 cm angular power spectrum from minihalos. We particularly focus on the
trispectrum of primordial curvature perturbations which are characterized by
the non-linearity parameters $\tau_{\rm NL}$ and $g_{\rm NL}$. We show that
future measurements of minihalo 21 cm angular power spectrum can probe these
non-linearity parameters with an unprecedented precision of $\tau_{\rm
NL}\sim30$ and $g_{\rm NL}\sim2\times10^3$ for Square Kilometre Array (SKA) and
$\tau_{\rm NL}\sim0.6$ and $g_{\rm NL}\sim8\times10^2$ for Fast Fourier
Transform Telescope (FFTT). These levels of sensitivity would give significant
implications for models of the inflationary Universe and the origin of cosmic
density fluctuations.
