A desulfurizing agent comprising a silica-alumina carrier having an Si/Al mole ratio of 10 or less and nickel carried thereon; a desulfurizing agent for hydrocarbons derived from petroleum which comprises a carrier and a metal component carried thereon and has a specific surface area of pores having a pore diameter of 3 nm or less of 100 m2/g or more; an Ni-Cu based desulfurizing agent comprising a carrier and, carried thereon, (A) nickel, (B) copper, and (C) an alkali metal or another metal; a desulfurizing agent for hydrocarbons derived from petroleum which comprises a carrier and a metal component carried thereon and has a hydrogen adsorption capacity of 0.4 mmol/g or more; and methods for producing these nickel-based and nickel-copper-based desulfurizing agents. The above desulfurizing agents are capable of adsorbing and removing with good efficiency the sulfur contained in hydrocarbons derived from petroleum to a content of 0.2 wt. ppm or less and have a long service life. The steam reforming of hydrocarbons derived from petroleum having been desulfurized by use of any one of the above desulfurizing agents allows the production of hydrogen for use in a fuel cell with good efficiency.