A braking system includes an electric motor configured to output a braking force, and a controller configured to control the electric motor. The controller is supplied with electric power from both a main power source and an auxiliary power source. The electric motor has a first state in which the electric motor is supplied with electric power from the main power source when the main power source has a voltage V1 equal to or higher than a threshold value Va; a second state in which the electric motor is supplied with electric power from the auxiliary power source, and the voltage V1 of the main power source is lower than the threshold value Va; and a third state in which the electric motor is supplied with electric power from the main power source, and the voltage V1 of the main power source is lower than the threshold value Va.