An apparatus for generating hydrogen including a housing, a reservoir, and a piston is provided. The housing has a top wall, a bottom wall, and a sidewall. The top wall has vents and a protrudent column extending to the interior of the housing. At least one vent communicates with the top wall and the protrudent column and rest of the vents surround the protrudent column. The reservoir is disposed in the housing for storing a solid state reactant and divides the housing into a first chamber and a second chamber. The first chamber is located between the top wall and the reservoir. The second chamber is located between the bottom wall and the reservoir for storing a liquid reactant. The piston is disposed on the bottom wall. The piston is used to push the liquid reactant towards the reservoir to react with the solid state reactant to generate hydrogen.