Provided are a method by which hydrogen can be continuously and efficiently produced through a dehydrogenation reaction of a formic acid solution even at a low concentration and/or low grade, and a system therefor. This method involves a reaction step for, while supplying formic acid, catalytically degrading the formic acid into carbon dioxide and hydrogen to thereby continuously produce hydrogen. This method is characterized by involving an extraction step for extracting formic acid from the formic acid solution serving as the starting material with the use of carbon dioxide obtained in the reaction step, and then supplying the formic acid to the reaction step.