The present invention is an exosome isolation method for obtaining high purity exosomes inexpensively from samples of large and small amounts and types of samples from which exosomes could not be obtained before such as plant lysates. The exosome isolation method incorporates a two phase fluid extraction system, and includes the steps of isolation using dextran and PEG for removing proteins and undesired substances therein, and the steps of washing and dextran removal to collect exosomes in a pure form.