A signal transmission device adapted to a camera includes a power input port, a boost converter, an Ethernet power circuit and a signal conversion circuit. The power input port is configured to receive an input power. The boost converter is configured to convert the input power to a boost power. The Ethernet power circuit is configured to output a DC power to the camera according to the boost power and to receive a data signal generated by the camera. The signal conversion circuit has a first interface electrically connected to the Ethernet power circuit and a second interface electrically connected to an operating system. The signal conversion circuit is configured to receive the data signal through the first interface and convert a format of the data signal, and further configured to transmit the converted data signal to operating system through the second interface.