A method for producing P1,P4-di(uridine 5'-)tetraphosphate (UP4U) that can avoid reduction of the synthetic efficiency without using UTP free is developed.A method for producing UP4U comprising reacting a phosphoric acid-activating compound represented by formula [II] or [III] with a phosphoric acid compound selected from the group consisting of UMP, UDP, UTP and a pyrophosphoric acid or a salt thereof (excluding UTP free) in water or a hydrophilic organic solvent, in the presence of a metal ion selected from the group consisting of an iron (II) ion, an iron (III) ion, a trivalent aluminum ion, a trivalent lanthanum ion, and a trivalent cerium ion.where, in the formula [II], R1 represents a uridyl group binding to the 5'-position, X represents a heterocyclic group, and n represents an integer of 1 or 2, where, in the formula [III], X represents a heterocyclic group selected from the group consisting of an imidazolyl group, a benzimidazolyl group, and a 1,2,4-triazolyl group.
