A method for manufacturing a precursor solution for forming a PZTN compound oxide with Pb, Zr, Ti and Nb as constituent elements by a sol-gel method includes: a step of dissolving at least lead carboxylate with an organic solvent having an alkoxy group, to thereby form a first solution; a step of heat treating the first solution to remove crystallization water of the lead carboxylate and to form lead alkoxide by a ligand replacement reaction between the lead carboxylate and the organic solvent having the alkoxy group, to thereby form a second solution including the lead alkoxide; a step of mixing an alkoxide of a metal selected from at least one of Zr, Ti and Nb excluding Pb with the second solution, to thereby form a third solution including metal alkoxides of Pb, Zr, Ti and Nb, respectively; and a step of adding water to the third solution to cause hydrolysis-condensation of the metal alkoxides, to thereby form a fourth solution including a precursor of PZTN compound oxide.