A vehicle inside mirror device employs a ball clamp in which a barrel-shaped ball clamp is prepared by assembling a pair of semi-barrel-shaped and symmetrical bodies to accommodate for manufacturing errors and the like. The ball clamp includes a mirror through which a driver can view rearwardly; and a mirror mounting part. The mirror mounting part has a barrel-shaped hinge part. A first ball clamp surrounds and clamps the hinge part. A second ball clamp corresponds to the first ball clamp with a spring between the first ball clamp and the second ball clamp for generating an expansion force. The mirror mounting part is fixed to a glass or a ceiling of a vehicle and has a hinge part for coupling the second ball clamp thereto. A tube surrounding the first ball clamp, the second ball clamp and the spring.