The effects of the leading quark mass corrections to the QCD sum rules for the 0⁺⁺ scalar glueball are investigated. In order to include the information from the confinement regions of QCD, the leading quark mass correction to the polarization function at Q²=0 for a renormalized group-invariant current with the quantum numbers J^PT= Phi ⁺⁺ are studied by means of the QCD low-energy theorem. For the construction of the corresponding spectral function, the authors use a 'finite-width resonance plus continuum' model in which the dynamical corrections due to the non-vanishing meson masses are taken into account. Two types of the QCD sum rules, namely the Gauss-Weierstrass finite-energy sum rules and the Laplace transform sum rule, are used to investigate the properties of the lowest 0⁺⁺ scalar glueball. The effects of the non-vanishing quark masses turn out to be not negligible for the determination of the glueball width; the intermediate value of the glueball mass is further confirmed by the leading quark mass correction.