PURPOSE: To provide a high resistance torque by coupling any one of an outer cylinder and a shaft body with a fixed member, and coupling the other with a rotating member.

CONSTITUTION: A slow-acting device 1 consists of a sealed outer cylinder 2, a shaft body 3 fitted inside of this outer cylinder 2 freely to rotate, a fin 4 connected to the outer cylinder 2, a fin 5 connected to the shaft body 3, and the fluid 6 (for example, viscous grease) filled inside of the outer cylinder 2. The outer cylinder 2 is fixed to a fixed member, and the shaft body 3 is coupled with a rotating member to perform the slow-acting function. The outer cylinder 2 and the shaft body 3 are rotated relatively by the rotation of the rotating member, and with this rotation, the fluid 6 between the fins 4, 5, which are respectively connected to the outer cylinder 2 and the shaft body 3, is compressed. A high resistance torque, which resists the rotation energy of the rotating member, can be thereby obtained. Furthermore, the number of parts is reduced to facilitate the assembly, and any type of a one-way and a two-way type devices can be obtained by changing the design slightly.