A vibration reducing device for a machine tool reduces vibration generated in a tool support body supporting a tool. The vibration reducing device includes an attenuation inducing member and a pressing and fitting mechanism. The attenuation inducing member is brought into contact with the tool support body so as to generate a frictional force in a direction in which it acts as a resistance to the vibration generated in the tool support body. The attenuation inducing member has a rigidity in a direction conforming to a contact surface between the attenuation inducing member and the tool support body, which rigidity is higher than that of the tool support body. The pressing and fitting mechanism fits the attenuation inducing member to the tool support body in a pressed condition.