A signal transmission device includes a signal side electrode; a first signal line connected to one side of the signal side electrode; a second signal line connected to the other side of the signal side electrode; a power source side electrode that forms a pair with the signal side electrode and is connected to the signal side electrode via an electronic component including at least an inductor component; and a capacitive coupling part that capacitively couples the power source side electrode to a ground wiring or a power source wiring. The first signal line, the signal side electrode, and the second signal line form a transmission path for transmitting an electric signal. The first signal line and the second signal line transmit power via the signal side electrode, the electronic component, and the power source side electrode.