Provided is a hydrogen reformer using exhaust gas, comprising: a catalytic reaction unit which generates a reforming gas containing hydrogen when exhaust gas generated in an engine and fuel are supplied thereto; and a heat exchange chamber which is mounted on an outer surface of the catalytic reaction unit and exchanges heat between the exhaust gas and the catalytic reaction unit to supply heat that is required for an endothermic reaction of the catalytic reaction unit, wherein heat of the exhaust gas is used for the endothermic reaction of a catalyst, such that a separate heat source for the endothermic reaction is unnecessary.