Highly conductive Nb doped SrTiO3 (Nb:STO) thin films with good crystallinity and smooth surfaces were epitaxially grown on SrTiO3 (STO) (1 0 0) substrates by laser molecular beam epitaxy. The resistivity, carrier concentration and mobility of the Nb:STO thin film are 3.6 x 10(-4) Omega cm, 2.8 x 10(21) cm(-3) and 12.7 cm(2)/V s, respectively, which are the best values in Nb:STO thin films reported so far. The root-mean-square surface roughness of the deposited thin him is measured to be 0.240 nm by atomic force microscopy. The chemical composition and its uniform distribution in the film were confirmed by angle-resolved X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. The difference of electronic structure in the band gap region between Nb : STO and STO thin films was studied by X-ray photoelectron spectroscopy.