A hydrogen generator (1) includes: a reformer which generates a hydrogen-containing gas from a raw material and steam; a combustor (4) which heats the reformer; an evaporator (2) which generates the steam by utilizing heat of a combustion gas after the reformer is heated by the combustion gas; and a control unit (20), the hydrogen generator (1) is controlled such that ON and OFF of a combustion operation of the combustor (4) are repeated in a start-up operation of the hydrogen generator (1) and a temperature of the reformer is kept to a predetermined temperature or lower, and the control unit (20) controls the combustion operation such that a heat amount per unit time by the combustor (4) in a first combustion operation is larger than the heat amount per unit time in k-th (k>1) and following combustion operations.