A portable cooler for cooling an article by utilizing the endothermic and exothermic phenomenon pertaining to a chemical reaction is disclosed, in which an adsorbent and a working medium are sealed in a reaction chamber defined between an inner wall and an outer wall, a working medium retaining member is disposed on the inner wall inside the reaction chamber for holding therein the working medium, the working medium retaining member being spaced from the adsorbent disposed on the outer wall, and a heater is held in contact with the adsorbent for regenerating the same, at least a part of said outer wall constituting a heat radiating portion.