PURPOSE: To provide a brake capable of obtaining sure braking force even continuous braking is applied for a long time, and also constant braking force even the brake is used for a long period.

CONSTITUTION: This device is composed of a negative pressure generation means 1, driven in relation to a rotary shaft 6; a tank 10, whose inside air is sucked by driving the negative pressure generation means 1; and a control valve 20, controlling air flowed into the tank 10. Closing the control valve 20, while driving the negative pressure generation means 1, generates vacuum pressure in the tank 10, applying brake to the rotary shaft 6 by the vacuum pressure via the negative pressure generation means 1.