The purpose of the present invention is to allow effective attenuation of rotation speed fluctuations over a wide range of rotational speeds with a compact configuration and without increasing the number of parts. This lockup device comprises a clutch (28), an intermediate member (30), an input-side damper mechanism (Di), an output-side damper mechanism (Do), and a dynamic damper device (33). The clutch (28) transmits the torque from a front cover (2) to the output side. The intermediate member (30) is disposed in a drive train between the clutch (28) and a turbine (4). The input-side damper mechanism (Di) is provided between the clutch (28) and the intermediate member (30) and attenuates rotational speed fluctuations. The output-side damper mechanism (Do) is provided between the intermediate member (30) and the turbine (4) and attenuates rotational speed fluctuations by generating hysteresis torque larger than the input-side damper mechanism (Di). The dynamic damper device (33) is coupled to the intermediate member (30) and attenuates rotational speed fluctuations.