  Let $N_{g,n}$ be a genus $g$ compact non-orientable surface with $n$
boundaries. We explain about relations on the level $d$ mapping class group
$\mathcal{M}_d(N_{g,0})$ of $N_{g,0}$ and the level $d$ principal congruence
subgroup $\Gamma_d(g-1)$ of $\mathrm{SL}(g-1;\mathbb{Z})$. As applications, we
give a normal generating set of $\mathcal{M}_d(N_{g,n})$ for $g\ge4$ and
$n\ge0$, and finite generating sets of $\mathcal{M}_d(N_{g,n})$ for some $d$,
any $g\ge4$ and $n\ge0$.
