A method for producing hydrogen by using different metals includes: providing a metal of lower reduction potential as an anode metal and a metal of higher reduction potential as a cathode metal, then immerse the anode metal and the cathode metal in an electrolyte, while the anode metal and the cathode metal can be combined with appropriate steps before or after being immersed in the electrolyte, whereby hydrogen and side-products generated from a reaction of electrochemistry caused by reduction potential difference between the different metals, that is, the method for producing hydrogen is through spontaneous chemical reaction without extra energy consumption.