Portable device (1 ) for producing hydrogen from a hydrogen precursor and a liquid, this device comprising - a main chamber (2), intended for receiving said hydrogen precursor and said liquid, - an additional chamber (6), intended for collecting the hydrogen thus produced, - a separation membrane (5), defining said main chamber relative to said additional chamber, - means (8) for discharging the hydrogen out of the additional chamber, and characterized in that it comprises heat exchange means (21), provided on at least one portion of the periphery of said main chamber. This device produces pure hydrogen which may supply a fuel cell.