To provide a system and a method for producing hydrogen which can be suitably used for efficiently producing hydrogen from a hydrocarbon fuel, particularly a real fuel, and helpful for effective use of the produced hydrogen.

The system comprises a collecting means for collecting a cycloparaffin from the hydrocarbon fuel, which is a real fuel, a reforming means for reforming the cycloparaffin by dehydrogenation, and a means for separating the hydrogen obtained by the reforming and a by-product hydrocarbon, wherein these means are allowed to communicate with each other in this order. The method for producing hydrogen and a by-product hydrocarbon comprises collecting a cycloparaffin from the hydrocarbon fuel and reforming the cycloparaffin by dehydrogenation.