A vibration-proof structure for a metallic electrical packaging case includes a metallic electrical packaging case and a coupling member. The coupling member connects an outer wall of the metallic electrical packaging case and a member forming a side wall of a vehicle. Also, the coupling member may include an engaging portion at one end of the coupling member, which is used for temporarily fixing the coupling member, and an insertion engaging portion, which is engaged with a portion of the member forming the side wall of the vehicle, formed at another end of the coupling member.