PURPOSE: To obtain an emergent brake device with a large emergent brake torque by installing a pressing operating part and a brake part in separation.

CONSTITUTION: When the first gear shaft 21 revolves in the C-direction and an allowable revolution speed is exceeded, the free edge side of a centrifugal piece 33 springs outwardly and turns around a supporting pin 34, against the springy force of a pulling spring 36, and the outer peripheral arcuate surface is press-attached onto the inner circumferential surface of the cylinder part 46b of a movable body 46. Therefore, the movable body 46 is turned in the C-direction, and an aslant surface part 46a is attached onto the aslant surface pat 45a of a fixed plate 45 and shifts in the getting- over D-direction, and is attached onto the frictional plate of a turning urging body 30 and applied with a turning moment in the C-direction, and kept in the self retention state at a turning position in the same direction. A movement receiving plate 47 is shifted in the same direction by the pressing shift in the D-direction of the movable body 46, and a pressing body 49 is shifted in the same direction through a belleville spring 50. Therefore, a pressure plate 58 presses a brake plate 56 and a pressing plate 59 through a receiving metal 60, and a brake torque is generated, and the turn of the rotary body is brake-appllied through a brake gear 53 and the first gear 21, and stopped.