A body (50) of a hydrogen generator of the present invention includes a reformer (10) configured to generate a reformed gas mainly containing hydrogen, a reforming material passage (1) configured to supply a reforming material, which is a material for a reforming reaction, to the reformer, a CO shifter (15) configured to convert CO contained in a reformed gas obtained from the reformer (10) into CO2, a reformed gas passage (2) configured to supply the reformed gas obtained from the reformer (10) to the CO shifter (15), and a passage (3) for the shifted gas obtained from the CO shifter (15). The shifted gas passage (3) and the reforming material passage (1) are adjacent to each other with a shared horizontal wall (31) interposed therebetween, and thereby, heat from the shifted gas and radiant heat from the downstream end face (15b) of the CO shifter are transferred to the reforming material that travels in the reforming material passage (1).