The preparation of the polycrystalline NdBa 2 Cu 3 O 7 - δ superconductor using Ba 2 Cu 3 O 5 + x as a precursor has been studied. Ba 2 Cu 3 O 5 + x was prepared by the sol-gel process using metal acetates as starting materials, tartaric acid as an chelating reagent and water as solvent. The gel was heated at 780°C for 60 h in O 2 to form the Ba 2 Cu 3 O 5 + x precursor. The value of x in Ba 2 Cu 3 O 5 + x was determined to be 0.5; that is, copper was in a highly oxidized state over +2. NdBa 2 Cu 3 O 7 - δ was obtained by the solid-state reaction between Nd 2 O 3 and Ba 2 Cu 3 O 5 + x heated at 900°C for 20 h in N 2 . Although the sample did not undergo post-anneal in oxygen, it showed good superconducting properties; T c of 94 K and the intragranular J c of 3.7 10 5 A/cm 2 under a field of 50 kOe at 20 K. The advantage of using Ba 2 Cu 3 O 5 + x is considered to be its sufficient amount of oxygen as well as prevention of the Nd 3 + /Ba 2 + substitution.