In the southern sky, there are many very high energy Galactic gamma-ray sources which have the possibility of cosmic-ray acceleration up to the PeV energy region (PeVatrons). Sub-PeV gamma rays are produced by interactions between PeV cosmic rays accelerated by PeVatrons and interstellar matter. Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA), consisting of an air shower array(83,000 $\rm{m^{2}}$) and underground muon detectors(3,600 $\rm{m^{2}}$) located at the Mt. Chacaltaya plateau(4,740 m), near La Paz, Bolivia, observes high energy cosmic rays and gamma rays with a wide field of view in the southern sky. The performances of ALPACA for gamma-ray source are estimated with a Monte Carlo simulation in this work. As a result, we expect to significantly detect the most promising PeVatron candidate, the Galactic Center.