The invention concerns a method and an apparatus for producing a metal hydroxide, in particular magnesium hydroxide, from a salt solution, wherein the metal is firstly precipitated from the salt solution and the suspension produced in that way is then filtered. The object of the invention is to provide a method and an apparatus which permit simple inexpensive and rapid production of metal hydroxide, in particular magnesium hydroxide, in a high state of purity. According to the invention that is achieved in that the suspension is filtered through at least one filter (13-17) of a cross-flow filtration installation (13-17), and that a permeate produced by filtration of the suspension is fed to the cross-flow filtration installation (14-17) again.