A manufacturing method of a planetary carrier (10, 10X, 10Y, 10Z), the planetary carrier (10, 10X, 10Y, 10Z) including a plurality of pinion gears (PG, PGa, PGb), a plurality of pinion shafts (PS, PSa, PSb) that are each inserted in a corresponding pinion gear (PG, PGa, PGb) of the plurality of pinion gears (PG, PGa, PGb), two supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) that each support a corresponding end portion of the pinion shafts (PS, PSa, PSb), and a plurality of bridge plates (15, 15X, 15Y, 15Z) that are each welded to the two supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) and that connect the two supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z), wherein the manufacturing method includes a blanking step of blanking each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) from a plate material (101, 102, 103, 104) so that each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) includes a plurality of peripheral portions (11e, 12e) that are extended linearly, and in the blanking step, each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) is blanked from the plate material (101, 102, 103, 104) so that one of the peripheral portions (11e, 12e) extends in parallel with an inner face (101hi, 102hi, 103hi, 104hi), corresponding to one of the peripheral portions (11e, 12e), of a blanked hole (101h, 102h, 103h, 104h) that is formed in the plate material (101, 102, 103, 104) by blanking of the supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) that has been performed one shot before, the two supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) include a first supporting plate (11, 11Y, 11Z) that has a first through hole and that supports one end of each of the pinion shafts (PS, PSa, PSb), and a second supporting plate (12, 12Y, 12Z) that has a second through hole and that supports the other end of each of the pinion shafts (PS, PSa, PSb), and in the blanking step, the first and second supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) are blanked from the plate material and the respective bridge plate (15, 15X, 15Y, 15Z) is blanked from a part of the plate material that corresponds to the first through hole and the second through hole. the manufacturing method includes a blanking step of blanking each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) from a plate material (101, 102, 103, 104) so that each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) includes a plurality of peripheral portions (11e, 12e) that are extended linearly, and in the blanking step, each supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) is blanked from the plate material (101, 102, 103, 104) so that one of the peripheral portions (11e, 12e) extends in parallel with an inner face (101hi, 102hi, 103hi, 104hi), corresponding to one of the peripheral portions (11e, 12e), of a blanked hole (101h, 102h, 103h, 104h) that is formed in the plate material (101, 102, 103, 104) by blanking of the supporting plate (11, 11Y, 11Z, 12, 12Y, 12Z) that has been performed one shot before, the two supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) include a first supporting plate (11, 11Y, 11Z) that has a first through hole and that supports one end of each of the pinion shafts (PS, PSa, PSb), and a second supporting plate (12, 12Y, 12Z) that has a second through hole and that supports the other end of each of the pinion shafts (PS, PSa, PSb), and in the blanking step, the first and second supporting plates (11, 11Y, 11Z, 12, 12Y, 12Z) are blanked from the plate material and the respective bridge plate (15, 15X, 15Y, 15Z) is blanked from a part of the plate material that corresponds to the first through hole and the second through hole.