We have investigated the de Haas-van Alphen effect in the Pr-based heavy-fermion superconductor PrOs4Sb12. The topology of Fermi surface is close to the reference compound LaOs4Sb12 and well explained by the band-structure calculation based on the FLAPW (full potential linearized augmented-plane-wave)-LDA (local-density approximation) +U method, where the 4f electrons are localized. We have confirmed a highly enhanced cyclotron effective mass (2.4-7.6)m(0), which is apparently large compared to the usual Pr-based compounds.