The high intensity positron source at the new research reactor FRM-II in Munich will be used to serve three instruments simultaneously: a scanning positron microscope, a pulsed positron beam and a system for positron induced Auger electron spectroscopy. In order to split the continuous beam into three parts with variable intensity, a beam splitter is being built. The device consists of an electrostatic optical system embedded in the constant magnetic guiding field of the beam line. In the first stage an electrostatic quadrupole is used to change the cross section of the beam into an ellipse. The resulting beam is then split into three parts by two pairs of deflection plates. The central part is transported to the microscope without deflection. The beam intensities can be varied by mechanical movement of the plates. At the exit port of the beam splitter the guiding magnetic field is split into three beamlines with the help of a magnetic shield made of mumetal.