A signal transmission device is provided. The signal transmission device comprises a linked unit, a data connector, a sliding block, a link and a lock block. The linked unit includes a first shaft, a second shaft, a third shaft, a first elastomer and a second elastomer. The data connector rotates and expands according to the first shaft and the first elastomer. During the retraction of the data connector, the data connector pushes the sliding block. Then the sliding block moves against the lock block so that the lock block rotates according to the second shaft. The lock block rotates to lock and secure the data connector by the lock piece, while a cam of the link moves to a secure location along an incline plane of a track of the sliding block.