A brake device and an automatic driving vehicle using the same are provided. The brake device includes an electrically controlled brake assembly, a mechanically controlled brake assembly and a shaft. The electrically controlled brake assembly has a main body and a brake control link. The shaft is connected between the electrically controlled brake assembly and the mechanically controlled brake assembly. The mechanically controlled brake assembly includes a pedal, an elbow, a brake link group and a brake pump. The first end is connected to the pedal, and the fulcrum is between the first end and the second end and is located close to the second end. The brake link group is connected between the elbow and the brake control link. The brake pump has an adjustable rod, and one link of the brake link group is connected to the adjustable rod.