To provide a brake device which can stop the rotational element surely when the external load in the prescribed direction and the opposite direction to the prescribed direction is operated for the rotational element and apply to the drive system for rotating and driving the rotational element in the prescribed direction and the opposite direction to the prescribed direction.

The brake device is provided with a first brake means 8 for braking the turning of the prescribed direction of a rotational element, a second brake means 10 for braking the turning of the opposite direction to the prescribed direction of the rotational element and an operation control means 168 for operating and controlling the first brake means and the second brake means. When the rotational control means stays on the operation position, the first brake means and the second brake means are not operated to the rotational elements 28, 30, 150, 152 and when the rotational control means stays on the non-operation position, the first brake means is operated and the turning of the rotational element is obstructed when the outside load of the prescribed direction is operated to the rotational element and the second brake means is operated and the turning of the rotational element is obstructed, when the external load of the opposite direction to the prescribed direction is operated to the rotational element.