In this study, in situ soft X-ray absorption spectroscopy (soft XAS) technique, which enables us to analyze electronic structures of oxides at elevated temperatures while controlling atmospheric conditions, was developed. The technique was applied to investigate the electronic structures of La0.6Sr0.4CoO3 (- delta). X-ray absorption spectra at the Co L-edges and the O K-edge were measured in the temperature range from room temperature to 873 K and the p(O-2) range from 10(-4) to 10(-2) bar. The developed in situ soft XAS technique is found to be effective for evaluating electronic structures of oxides under controlled temperature and p(O-2). (C) 2014 Elsevier B.V. All rights reserved.