A motor brake device of an exercise apparatus includes a motor, a brake device and a lifting device. The brake device has a rotating disc and a magnetic brake mechanism. The rotating disc is coaxially mounted on a motor shaft of the motor. The magnetic brake mechanism has at least one magnetic portion. The lifting device is configured to drive the magnetic brake mechanism to move between a first position where the magnetic portion is located close to the rotating disc and a second position where the magnetic portion is located away from the rotating disc. The second position is located higher than the first position. When there is no electric power supplied to the exercise apparatus, the magnetic brake mechanism can move downward to the first position to stop rotation of the motor shaft by gravity due to potential difference between the second position and the first position.