Effects of magnetic field on the electroless nickel/cobalt deposition using electroless nickel/gamma-Al2O3 as the support and a hypophosphite ion as the reducing agent in the alkaline solution were studied. The active sites for electroless nickel/cobalt deposition were divided into three types in which the first type of active sites were occupied by both nickel ion and cobalt ion and the second and third types of active sites were occupied by the hypophosphite ion. Three exponential equations for the rate constants of nickel, cobalt, and hypophosphite ions were obtained, respectively. The plots of logarithms of rate constants were linear with the square of magnetic flux density. Based on the results of hydrogen gas evolution rate, the recombinations of Ni(+)a(.)/H-a(.) and Co+./H-a(.) radical pairs were affected by the magnetic field; however, the H-a(.) radicals did not separate from these radical pairs.