  We propose $q$-deformation of the Gamayun-Iorgov-Lisovyy formula for
Painlev\'e $\tau$ function. Namely we propose formula for $\tau$ function for
$q$-difference Painlev\'e equation corresponding to $A_7^{(1)}{}'$ surface (and
$A_1^{(1)}$ symmetry) in Sakai's classification. In this formula $\tau$
function equals the series of $q$-Virasoro Whittaker conformal blocks
(equivalently Nekrasov partition functions for pure $SU(2)$ 5d theory).
