The present invention provides a high purity heparin useful as a medicine a cosmetic a research reagent and the like and a production method therefor in more detail a method for producing heparin the method comprising mixing a heparin without substantially containing nitrous acid degradation resistant impurities with 0.2 to 1 time (volume) the amount of ethanol to 5 to 30 wt% of heparin solution and obtaining a colloidal precipitate of heparin.