PROBLEM TO BE SOLVED: To provide a bone joining plate processing tool for facilitating the processing of a bone joining plate.SOLUTION: The processing tool 10 includes: a reception part 12 for supporting the bone joining plate 50 a pressing part 14 facing the reception part 12 a heater for heating the reception part 12 and the pressing part 14 and grip parts 16a, 16b to be gripped by hand when operating the processing tool 10. Since the tool includes multiple work parts 22a, 22b, 22c with the combination of planes and curved surfaces, steps d1, d2 and circular arcs are formed in the bone joining plate 50.