Ethanol obtained from ordinary biomass resources contains many impurities other than water and these impurities themselves or their decomposition products contaminate ethylene when the ethylene is produced by a dehydration reaction, whereby the activity of metathesis catalyst is adversely affected. A method for producing propylene of the present invention is characterized in that the ethanol obtained from biomass is converted to ethylene by a dehydration reaction, the ethylene is separated from the generated water, the separated ethylene is purified by adsorption in an adsorption tower filled with an adsorbent, and then a metathesis reaction is carried out along with a raw material containing n-butene. With the present invention, propylene having biomass-derived carbon and reduced-environmental burden can be efficiently produced without lowering the catalysis activity.