PURPOSE: To prevent fluctuation of ratio of methanol vapor to steam, to prevent deterioration of reforming catalyst, and to produce H2 stably for a long period by allowing methanol vapor and steam, which have been evaporated separately and controlled to respective flow rate, to react with each other.

CONSTITUTION: Feed methanol is introduced into a methanol tank 1, then fed to a methanol evaporator 3 with a pump P and transformed to methanol vapor. On one hand, pure water to be fed is introduced into a pure water tank 2, then fed to a circulated water evaporator 4 through a washing tower 7 with the pump P, and transformed to steam. Flow rates of the methanol vapor and the steam are controlled by each flow rate control valve V separately, and mixed to attain a specified steam/methanol ratio, and the mixture is fed to a feed superheater 5, and then fed to a reformer 6 to reform thus the methanol with the steam thus producing H2. Obtd. reaction mixture is washed in a washing tower 7 with pure water, and H2-rich gas is recovered.