It is required to get large working space when the parallel mechanism based machine tools are used. However, the shape of working space is considerably complicated because of the influence of the self-interference generated between the parts and of singular points. In this paper, an analysis system for calculating the working space of parallel mechanism based machine tools is developed. It can be adapted to various types of parallel mechanism based machine tools including tilting type, perpendicular type, telescopic type and revolving type. Taking HexaM machine developed by Toyoda Machine Works Co. as the model, the developed software is proved to be effective by comparing the results of experiment and simulation. Moreover, the HexaM machine is evaluated by investigating the influence of the shape and dimension of parts on the working space.