The unoccupied electronic structure in the surface state of lightly doped SrTiO3 has been studied by resonant inverse-photoemission spectroscopy (RIPES). The RIPES spectra show two features whose energy separations match the t2g and eg subbands of unoccupied Ti 3d state. A peak clarified by the Ti 3p → 3d resonance effect is observed at -6.1 eV above Fermi level (EF). The -6.1 eV peak is not found in the O 1 s x-ray absorption spectrum, which reflects the electronic structure of the bulk state. The existence of the -6.1 eV peak suggests the correlation effect in the surface state of lightly doped SrTiO3.