Exosome isolation method by two phase fluid system, which enables to obtain exosome from cytoplasm inner and outer fluids, comprising the steps of a. preparing a fluid sample containing exosomes, b. removing the contaminants in the fluid sample, c. mixing the fluid sample with the isolation solution containing PEG and dextran in distilled water, d. separating the mixture formed for isolation into two phases by means of the two phase fluid extraction system, e. discarding the supernatant of the sample, which is separated into two phases, in order to remove the proteins and other undesired substances therein, f. mixing the collected the phase with a washing solution using PEG in water, g. separating the mixture formed for washing into two phases by means of the two phase fluid extraction system, h. discarding the supernatant of the two phases that are formed and collecting the lower phase containing the exosome, is characterized in that the step h) is followed by a dextran removal method for removing dextran from the obtained exosome solution, comprising the sub-steps of; i. adding the purification solution containing monohydric alcohol or acetone in order to remove dextran from the collected lower phase, ii. removing dextran from the collected lower phase via filtration, iii. removing the dextran that is precipitated by the purification solution from the exosomes, iv. removing the purification solution from the exosomes thereby obtaining exosomes in pure form, wherein the centrifugation method is used for removing dextran from the exosomes. a. preparing a fluid sample containing exosomes, b. removing the contaminants in the fluid sample, c. mixing the fluid sample with the isolation solution containing PEG and dextran in distilled water, d. separating the mixture formed for isolation into two phases by means of the two phase fluid extraction system, e. discarding the supernatant of the sample, which is separated into two phases, in order to remove the proteins and other undesired substances therein, f. mixing the collected the phase with a washing solution using PEG in water, g. separating the mixture formed for washing into two phases by means of the two phase fluid extraction system, h. discarding the supernatant of the two phases that are formed and collecting the lower phase containing the exosome, is characterized in that the step h) is followed by a dextran removal method for removing dextran from the obtained exosome solution, comprising the sub-steps of; i. adding the purification solution containing monohydric alcohol or acetone in order to remove dextran from the collected lower phase, ii. removing dextran from the collected lower phase via filtration, iii. removing the dextran that is precipitated by the purification solution from the exosomes, iv. removing the purification solution from the exosomes thereby obtaining exosomes in pure form, wherein the centrifugation method is used for removing dextran from the exosomes. i. adding the purification solution containing monohydric alcohol or acetone in order to remove dextran from the collected lower phase, ii. removing dextran from the collected lower phase via filtration, iii. removing the dextran that is precipitated by the purification solution from the exosomes, iv. removing the purification solution from the exosomes thereby obtaining exosomes in pure form, wherein the centrifugation method is used for removing dextran from the exosomes.