Abstract: An arm vibration damping device, comprising a housing (9), a longitudinal vibration damping module (1) and a transverse vibration damping module (2), the longitudinal vibration damping module (1) comprising a longitudinal motor (11), a support frame (12) and a mounting frame (13), the mounting frame (13) comprising a U-shape element (131) and a mounting element (132); the support frame (12) being located between the U-shape element (131) and two arms, the longitudinal motor (11) being in a transmission connection with the U-shape element (131); a transverse motor (21) of the transverse vibration damping module (2) being in a transmission connection with the support frame (12) via a reverse mechanism (22); the transverse motor (21), the support frame (12), the U-shape element (131) and the mounting element (132) being arranged along an axial direction of the transverse motor (21).