The invention discloses a brake and an electrically controlled actuator. The brake comprises a driving mechanism, a planetary wheel transmission mechanism, an output gear and an output shaft; the output gear is fixed to the output shaft; and the first end of the planetary wheel transmission mechanism is connected with the driving mechanism, the second end of the planetary wheel transmission mechanism is connected with the output gear to enable the driving mechanism to drive the first end of the planetary wheel transmission mechanism, and thus the second end of the planetary wheel transmissionmechanism drives the output gear to axially rotate around the output shaft so as to drive the output shaft to rotate. According to the brake and the electrically controlled actuator, the purpose of effectively decreasing the overall brake volume is achieved, and thus the technical effect that the overall structure of the brake is more compact is achieved.