Surface structures and electronic properties of submonolayer sulfur dioxide SO2 molecularly adsorbed on Ni(111) and Ni(100) have been investigated by means of S K-edge SEXAFS, S and O K-edge NEXAFS, S 1s and 2p XPS, UPS, and ab initio SCF-MO calculation. S K-edge NEXAFS and SEXAFS have clarified that on both surfaces the SO2 molecule adsorbs with the molecular plane parallel to the surface and with the bridge site occupation of the S atom. The SCF-MO calculation has verified such a flat-lying structure. Charge transfer from the Ni 3d band to the SO2 pi* orbital has also been elucidated by S and O K-edge NEXAFS, S 1s and 2p XPS, UPS and the SCF-MO calculation.