A reformer (10) for a fuel cell has a chamber (26) including a chamber inlet (20) for the input of a reactant gas mixture and a chamber outlet (24) for the output of a reformed gas, a catalytic active medium being arranged in the chamber. The reformer (10) has a heat pipe (12) with an outer cylindrical pipe wall (14) and an inner cylindrical wall (16), the chamber (26) being disposed between the outer pipe wall (14) and the inner wall (16). Advantageously, the heat pipe has a passage with a helical shapes.