An Instrument for an exotic particle search (INSTEPS) in cosmic rays is proposed for detailed investigation of cosmic ray flux in the charge region 0.5 - 2 minimum-ionizing particles (mip), where a few strange results have been registered. These results could not be understood because of poor charge resolution. There is also 0.1 - 0.5 mip region, which is practically unknown because of a limited signal to noise ratio. The instrument includes a set of self-triggered modules with 6 layers of 1 mm thick silicon microstrip detectors 10 x 10 cm^2 size for precise charge measurements. Every module can be also used as a separate device in many other experiments where precise charge determination is required. For exotic particle search a group of the charge measuring modules is placed on the top of a scintillator calorimeter. The calorimeter will measure particle energy and trajectory and generate a special trigger for the charge modules when the energy is above 50 GeV. This serves to decrease particle flux, because the already mentioned anomalies have been observed between high energy hadrons. We plan to expose the instrument at mountain level where it can register the particles that have arrived from space as well as those generated in the atmosphere.