An optical member driving mechanism is provided. The optical member driving mechanism includes a movable portion and a fixed portion. The movable portion includes a holder for holding an optical member with an optical axis. The movable portion is movable relative to the fixed portion. The fixed portion has a housing and a base. The housing is disposed on the base, and includes a top surface and a side surface. The top surface extends in a direction that is parallel to the optical axis. The side surface extends from an edge of the top surface in a direction that is not parallel to the optical axis. The side surface has a rectangular opening.