A hydrogen generator includes: a water evaporation unit configured to mix water with a raw gas; a burner; a combustion exhaust gas flow channel provided on an inner side than the water evaporation unit and through which a combustion exhaust gas from the burner flows; a reforming catalyst layer configured to produce a reformed gas; and a carbon monoxide reduction unit configured to reduce an amount of carbon monoxide contained in the reformed gas. The water evaporation unit includes a flow channel member defining a flow channel through which the raw gas and the water flow. A pitch of the flow channel member is changed according to at least one of an amount of heat exchange between the combustion exhaust gas flow channel and the water evaporation unit and an amount of heat exchange between the water evaporation unit and the carbon monoxide reduction unit.