Provided is a viscous fluid-sealed damper which helps to achieve an increase in degree of freedom in terms of the selection of the material of a sealing container, which can be produced with high production efficiency, and which helps to avoid leakage of the viscous fluid. A lid member is fixed to a container main body while compressing and holding a flange portion between a sealing member and the lid member, so an opening end of the container main body can be sealed with the lid member without having to effect fixation through fusion-bonding as in the prior art, and the degree of freedom in terms of material selection can be increased. Further, if the container main body is formed of a butyl rubber, the container main body can be fixed to the lid member without using any adhesive, so it is possible to achieve a reduction in production time and in cost. Further, it is possible to avoid leakage of the viscous fluid due to defective adhesion.