We simulated quartz-type GeO2 and investigated its high-pressure transformation using the molecular dynamics (MD) simulation method with a model potential, The calculated results under hydrostatic compression indicated that a pi pressure-induced amorphization of quartz-type GeO2 originated from the mechanical instability of the quartz lattice as, in previous theoretical studies of SiO2. Furthermore, quartz-type GeO2 directly transformed to a rutile-like structure with only subtle displacements of ions under sigma(xy) imposed shear stressed decompression. This is the first reproduction of the quartz-to-rutile transformation. A possible pathway of this transition is proposed in this study.