We report the first experimental demonstration of an electrostatic electron orbital angular momentum (OAM) sorter, which can be used to analyze the OAM states of electrons in a transmission electron microscope. We verify the sorter functionality for several electron beams possessing different superpositions of OAM states, and use it to record the electron beams OAM spectra. Our current electrostatic OAM sorter has an OAM resolution of 2 in the units of h/bar-the reduced Planck constant. It is expected to increase the OAM resolution of the sorter to the optimal resolution of 1 in the future via fine control of the sorting phase elements.