q-Heun equation and initial-value space of q-Painlev\'e equation

We show that the q-Heun equation and its variants appear in the linear q-difference equations associated to some q-Painlev'e equations by considering the blow-up associated to their initial-value spaces. We obtain the firstly degenerated Ruijsenaars-van Diejen operator from the linear q-difference equation associated to the q-Painlev'e equation of type $E_8$.