To provide a chain drive device capable of attenuating cord vibration in a tension side span of a chain without generating friction loss.

This chain drive device 1 is provided with a chain 4 wrapped around a drive sprocket 2 and a follower sprocket 3, and an attenuator 5 disposed on the tension side span 40 of the chain 4 to get in contact with the tension side span 40 with no clearance to be applied to the tension side span 40 when the tension span 40 resonates to apply attenuation force to the tension side span 40. The attenuator 5 comprises a blade shoe 50 having a chain abutment surface 50a, a plurality of blade springs 51, and a base member 52 having a slide surface 52a to slidably support a tip part 50d of the blade shoe 50, and a support shaft part 52b to rotatably support a base end part 50e of the blade shoe 50.