The present invention concerns a method and apparatus of decoding a one-point algebraic geometric code defined on an algebraic curve represented by an equation in X and Z of degree 2.sup..mu..phi. in Z, where .phi. is a strictly positive integer and .mu. an integer greater than 1, obtained by taking the fiber product of .mu. component algebraic equations, each of said component equations governing the unknown X and an unknown Y.sub.i, where i=0, . . . , .mu.-1, and being of degree 2.sup..phi. in Y.sub.i. This method comprises the decoding of 2.sup.(.mu.-1).phi. "clustered" codes, all defined on the same algebraic curve represented by one of said component equations.