A metal phosphate having high proton conductivity which is useful for a fuel cell having higher output, and a method for producing such a metal phosphate are provided. The method for producing a metal phosphate is a metal phosphate production method using a compound containing M, a compound containing J 1 , and a compound containing P, as raw materials, wherein M represents at least one selected from the group consisting of group 4A and group 4B elements in the long form of the periodic table, J 1 represents at least one selected from the group consisting of group 3A, group 3B, group 5A and group 5B elements in the long form of the periodic table, the compound containing J 1 is composed of at least one selected from hydroxides of J 1 , halides of J 1 and nitrate of J 1 .