Pressure effects on the recently discovered BiS2-based superconductor Bi-2(O,F)S-2 (T-c = 5.1 K) were examined by two different methods: high-pressure resistivity measurement and high-pressure annealing. The effects of these two methods on the superconducting properties of Bi-2(O,F)S-2 were significantly different, although in both methods, hydrostatic pressure is applied to the sample using a cubic-anvil-type apparatus. In high-pressure resistivity measurement, T-c linearly decreased at a rate of -1.2KGPa(-1). In contrast, the T-c of 5.1K is maintained after high-pressure annealing under 2 GPa and 470 degrees C of an optimally doped sample despite a significant change in lattice parameters. In addition, superconductivity was observed in fluorine-free Bi2OS2 after high-pressure annealing. These results suggest that high-pressure annealing has a unique effect on the physical properties of layered compounds.