We have investigated trapping effects of monoatomic vacancies Vmono and alloy atoms on hydrogen diffusion at Al(111) surfaces. We performed first-principles calculations based on density functional theory with generalized gradient approximation in order to obtain the hydrogen adsorption energies in the vicinity of monoatomic vacancies and alloy atoms in Al(111) subsurfaces. We considered Si, Cr, Mn, Fe, Cu, Ge, and Zn as alloy atoms. We substituted one Al atom with one monoatomic vacancy or alloy atom, which corresponds to Al0.95X0.05(111) (X=Si, Cr, Mn, Fe, Cu, Ge, Zn, Vmono) surfaces. We found that all of monoatomic vacancies and alloy atoms increase adsorption energies. We also clarified that hydrogen atoms make strong covalent bonds in Cr, Mn, Fe-alloyed Al(111) subsurfaces, while they make only weak ionic bonds in pure and Si, Cu, Ge, Zn-alloyed Al(111) subsurfaces.