To provide a cladding tube for nuclear fuel capable of prolonging reactor operation for attaining high burnup and maintaining sufficient corrosion resistivity against multiplier effect of electrochemical interaction between different metals and variation of reactor water quality.

A portion of the cladding tube for nuclear fuel held by fuel support grids and a range in 0 to 20 mm to upward and downward from the portion where coating film forming region 16a is formed are positioned in solution tanks 21A to 21N. Electrolyte 31 is injected in the solution tanks 21A to 21N. An anode side and a cathode side of a direct current source 32 are electrically connected with the coating film forming region 16a and solution tanks 21A to 21N, respectively. By energizing current for a specific time, a coating film consisting of metal oxide with a thickness of ca. 0.5 μm is formed in the coating film forming region 16a.