A hydrogen generating apparatus comprising: an evaporator configured to generate a mixture gas by mixing a source gas containing methane with water vapor; a reformer configured to convert the mixture gas to hydrogen-containing gas by a steam reforming reaction; a combustor configured to supply heat to the evaporator and the reformer, a shift converter configured to decrease concentration of carbon monoxide in the hydrogen-containing gas, a CO remover configured to remove the carbon monoxide from the hydrogen-containing gas wherein the evaporator comprises an inner cylinder, an outer cylinder surrounding the inner cylinder, and a center cylinder inserted between the inner cylinder and the outer cylinder, the center cylinder defining, between the inner cylinder and the outer cylinder, a spiral channel configured to allow water supplied from outside to flow, a length in a direction of the gravitational force of the evaporator being 300-400mm, the reformer being disposed in a lower side in the direction of the gravitational force of the evaporator and surrounding the inner cylinder, the shift converter surrounding a region of lower part in the direction of the gravitational force of the evaporator, the CO remover being connected to the shift converter and surrounding a region of upper part in the direction of the gravitational force of the evaporator, and the combustor being disposed in a heat chamber disposed in the inner cylinder, a spiral protrusion and a spiral recess, the spiral protrusion and the spiral recess formed on an inner circumference surface and an outer circumference surface of the center cylinder in such a unitary manner that one of the spiral protrusion and the spiral recess serves as the other on one of inner circumference surface and outer circumference surface of the center cylinder and vice versa, a top surface of the protrusion on the inner circumference surface of the center cylinder comes in surface contact with an outer circumference surface of the inner cylinder, and a top surface of the protrusion on the outer circumference surface of the center cylinder comes in surface contact with an inner circumference surface of the outer cylinder, and wherein recess on the outer circumference surface of the center cylinder constitutes evaporation channel and pitch P1 of the evaporation channel in the upstream side is smaller than pitch P2 of the evaporation channel in the downstream side. an evaporator configured to generate a mixture gas by mixing a source gas containing methane with water vapor; a reformer configured to convert the mixture gas to hydrogen-containing gas by a steam reforming reaction; a combustor configured to supply heat to the evaporator and the reformer, a shift converter configured to decrease concentration of carbon monoxide in the hydrogen-containing gas, a CO remover configured to remove the carbon monoxide from the hydrogen-containing gas wherein the evaporator comprises an inner cylinder, an outer cylinder surrounding the inner cylinder, and a center cylinder inserted between the inner cylinder and the outer cylinder, the center cylinder defining, between the inner cylinder and the outer cylinder, a spiral channel configured to allow water supplied from outside to flow, a length in a direction of the gravitational force of the evaporator being 300-400mm, the reformer being disposed in a lower side in the direction of the gravitational force of the evaporator and surrounding the inner cylinder, the shift converter surrounding a region of lower part in the direction of the gravitational force of the evaporator, the CO remover being connected to the shift converter and surrounding a region of upper part in the direction of the gravitational force of the evaporator, and the combustor being disposed in a heat chamber disposed in the inner cylinder, a spiral protrusion and a spiral recess, the spiral protrusion and the spiral recess formed on an inner circumference surface and an outer circumference surface of the center cylinder in such a unitary manner that one of the spiral protrusion and the spiral recess serves as the other on one of inner circumference surface and outer circumference surface of the center cylinder and vice versa, a top surface of the protrusion on the inner circumference surface of the center cylinder comes in surface contact with an outer circumference surface of the inner cylinder, and a top surface of the protrusion on the outer circumference surface of the center cylinder comes in surface contact with an inner circumference surface of the outer cylinder, and wherein recess on the outer circumference surface of the center cylinder constitutes evaporation channel and pitch P1 of the evaporation channel in the upstream side is smaller than pitch P2 of the evaporation channel in the downstream side.