A transmission device applied to a pivot shaft mechanism provides a security system and is easy to assemble. The transmission device includes at least one rotary shaft, a drive section movable with the rotation of the rotary shaft, a driver (transversely) reciprocally movable and a turning unit having a first end connected with the driver and a second end assembled with a carrier body. The driver includes an arm section provided with an elastic body and a hand section connected with the arm section. When the driver is transversely moved, the turning unit is swung, whereby the second end of the turning unit drives the carrier body for lifting or lowering a substrate body or a frame in accordance with the operation mode of an electronic apparatus.