We demonstrated that rare gas (RG) occluded in the C-60 lattice has a chemical interaction with C-60 . In order to evaluate the interaction between RG and C-60 , we calculated the electronic state of C-60 (RG) n (n=1,2,3) crystals. RG atoms in C-60 (RG) (RG=He, Ne, Ar) are neutral, whereas those in C60Kr and C60Xe have positive Mulliken charges of 0.99 and 1.04, respectively. For C-60 (RG)(2) and C-60 (RG)(3) , a slightly positive charge of 0.02 appeared on Ar atom in C60Ar2 and C-60 Ar-3 . The chemical reaction such as a hydrogenation of CO to CH4 was found to occur in the nanospace of C-60 -sodium-hydrogen.