A method for acquiring an unbalance amount of a rotor, and a method for acquiring an unbalance amount of a balancing machine. The method for acquiring an unbalance amount of a rotor comprises the following steps: mounting an angle sensor on a balancing machine at a first position on the balancing machine, measuring an unbalance amount of a rotor, and performing measurement to obtain a first unbalance amount of a first measurement plane and a first unbalance amount of a second measurement plane (B); moving the angle sensor on the balancing machine from the first position to a second position on the balancing machine (C); performing another measurement of the unbalance amount of the rotor, and obtaining a second unbalance amount of the first plane and a second unbalance amount of the second plane (D), wherein in the above two unbalance amount measurement operations, the magnitude of the unbalance amount of the rotor does not change, and an angle of the unbalance amount relative to a reference point on the rotor changes a movement angle of the angle sensor (E), and in addition, a magnitude and an angle of an unbalance amount of the balancing machine itself remain unchanged (G); and acquiring the unbalance amount of the rotor by means of vector calculation (H). The method provides simple measurement and accurate detection.