In a manufacturing method of a rotor for an electric motor including: a core (4) formed of stacked steel plates, each of which has a center hole (4a); and a shaft (3) inserted through the center hole (4a) of the core (4), the shaft (3) is deformed to fit a second end plate (2) in a state where the second end plate (2) is pressed against the core (4), and a deformed portion (3e) of the shaft (3) that engages with an edge (2a, 2b) of the second end plate (2) is deformed along a core-side edge portion (2a) and a no core-side edge portion (2b) of the edge (2a, 2b) of the second end plate (2) so that the deformed portion (3e) is deformed into the deformed shape that fits the shape of the edge (2a, 2b) of the second end plate (2).