According to the invention, there is provided a carriage arm assembly including a carriage arm having two arm members. The arm member is constructed in such a way that the width of its coil side end and the width of its suspension side end are narrower than that of its intermediate area. This construction widens a servo band width, improves positioning accuracy, and reduces positioning errors of a magnetic disk apparatus, so that recording density is improved and storage capacity is increased. Further, by coupling two arm members using a restriction member via a visco-elastic member, it is possible to achieve a high damping effect on various vibration modes including in-plane bending of the arms, and suppress vibration of the carriage so as to reduce the positioning errors.