Provided is a hydrogen generator which can flexibly respond to the change of supply quantity of hydrogen, and particularly, can easily respond to hydrogen mass production and can generate highly purehydrogen in high yield. A hydrogen generator 1 generates hydrogen gas from raw material gas in high yield through decomposition by a catalyst and plasma gasification of the raw material gas by electric discharge. The hydrogen generator 1 comprises: a dielectric 2 that defines a raw material gas flow path 13; a catalyst 10 that generates hydrogen gas by decomposing at least part of raw material gasflowing through the raw material gas flow path 13; an electrode 3 that is disposed so as to be in contact with the dielectric 2; a hydrogen separation membrane 5 that faces the electrode 3 via the dielectric 2; a hydrogen flow path 18 through which hydrogen separated by the hydrogen separation membrane 5 is delivered; and a high voltage power source 6 that supplies electric power so as to generate electric discharge between the hydrogen separation membrane 5 and the electrode 3.