NOVELTY - A hydrogen generating device (1) includes a reforming unit comprising a first path plate having first penetration grooves, first walls, an alumina layer, and a first catalyst layer; and a second path plate having second penetration grooves, second walls, and a second catalyst layer. The first walls are inserted into the second penetration grooves, and the second walls are inserted into the first penetration grooves. The first walls and second walls are located opposite to each other and spaced apart from each other by not greater than 500 microns, respectively.    USE - For use in fuel cell system.    ADVANTAGE - The device has small size and improved reforming rate. Since the reforming rate is improved, the hydrogen generation efficiency of the hydrogen generating device is enhanced and the power generation efficiency of the fuel cell system is improved.    DETAILED DESCRIPTION - A hydrogen generating device includes a reforming unit to obtain reformed gas containing hydrogen from a fuel containing dimethyl ether and water. The reforming unit comprises a first path plate having first penetration grooves adjacent to one another, first walls defining the first penetration grooves, an alumina layer formed by anodic oxidation of the surface of first walls, and a first catalyst layer containing heteropolyacid carried on the alumina layer; and a second path plate arranged opposite to the first path plate and having second penetration grooves formed to correspond to the first penetration grooves one by one, second walls defining the second penetration grooves, and a second catalyst layer formed of the surface of second walls. The first walls are inserted into the second penetration grooves, and the second walls are inserted into the first penetration grooves. The first walls and second walls are located opposite to each other and spaced apart from each other by not greater than 500 microns, respectively. An INDEPENDENT CLAIM is included for a fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure is a block diagram of a fuel cell system.    Hydrogen generating device (1)    Fuel cell (2)    Proton conductive electrolyte membrane (2c)    Fuel supply mechanism (3)    Pump (9)    Insulating unit (10)