A process for efficiently and economically producing a nucleoside-5'-phosphate which comprises treating a nucleoside and a phosphoric acid donor selected from the group consisting of poly-phosphoric acid (salts), phenylphosphoric acid (salts) and carbamylphosphoric acid (salts) with an acid phosphatase, in particular one suffering from a decrease in the nucleotidase activity, at a pH value of 3.0 to 5.5 to thereby form a nucleoside-5'-phosphate and taking up the same.
