A method for forming roughness on an outer surface of cladding of a fuel nuclear rod including zirconium includes: positioning the cladding of the nuclear fuel rod at a first electrode and connecting a positive electrode thereto, and positioning a conductive plate at a second electrode and connecting a negative electrode thereto; putting the cladding of the nuclear fuel rod in an electrolyte solution; and applying voltage to the positive electrode and the negative electrode to cause oxidation on the outer surface of the cladding of the nuclear fuel rod. In this case, the electrolyte solution is maintained at 10° C. or lower.