PURPOSE: To provide a magnesium compsn. obtd. from natural raw materials which contain relatively much magnesium and which themselves can be used as food additives among natural raw materials contg. magnesium and a process for producing this compsn.

CONSTITUTION: The coral sand obtd. from the nature is dissolved with a hydrochloric acid in a dissolving stage ST11 and thereafter, this dissolved liquid is filtered in a filtering stage ST12 and insoluble components are removed therefrom to obtain a filtrate. Next, a neutralizing agent, such as sodium hydroxide, is added to this filtrate to neutralize the filtrate in a neutralizing stage ST13. The filtrate is again filtered in a filtering stage ST14, by which a soln. contg. the much magnesium hydroxide is obtd. The filtrate is dried to obtain the powder of the magnesium hydroxide and thereafter, this powder is subjected to a heat treatment in a thermal decomposition stage ST15, by which the magnesium hydroxide powder (magnesium compsn. for drink and food additives) is obtd.