The COMMON DATA PROCESSING SYSTEM (Ver. 3.0), which is software for common handling of spectral data taken on different instruments, has been constructed using Visual Basic language under MS-Windows (3.1). This software is used to convert each file format to the common format proposed as "VAMAS-SCA Standard Data Transfer Format," to obtain the characteristic parameters of one’s spectrometer by using standard spectra in the system, to calibrate a spectrum with those parameters, to analyze spectral data by proposed procedures, and to obtain correction factors from the database. The COMMON DATA PROCESSING SYSTEM is not commercially produced but should be created by all the scientists and engineers who have an interest in promoting surface analysis. The fruits of the VAMAS-SCA activities have been made available with this software.