Abstract: X-ray photoelectron spectroscopy (XPS), also called electron spectroscopy for chemical analysis (ESCA), is widely used both in basic research and in analysis of materials, particularly in surface analysis. Using XPS we can obtain information on the elemental surface composition (except for H and He), and the electronic structure of the materials involved. This paper will briefly review the principle of XPS, basic qualitative and quantitative data analysis methods, and some application examples.