Since March 2015, when the source codes of Mass++ became open, the Mass++ Users Group has continued working on the improvement of its peak detection function; this year, a new plug-in was developed for utilizing ProteoWizard. ProteoWizard is an open-source program and the characteristics of its peak detection function is the ability for correcting the precursor ion mass values. By using this function, great improvement of database search results is expected; Mass++ can utilize this function with graphical interface. Evaluation tests using the comprehensive human serum proteome data showed improvement in the number of identified proteins. Detailed information about Mass++ can be obtained from http://www.mspp.ninja/, and the installable package can be downloaded from http://mspp.osdn.jp/.