A signal transmission device and a battery monitoring device are provided. The signal transmission device is connected to an operation device including an operation circuit for performing an operation based on a first voltage, a measurement circuit for obtaining measurement data based on the first voltage, and a process control circuit for operating based on a lower voltage and control an operation of the operation circuit based on the measurement data, and transmits and receives signals between the process control circuit and the measurement circuit. The signal transmission device includes a power reception circuit for supplying power from the power transmission circuit to the measurement circuit to acquire measurement data, and a power transmission circuit for transmitting the power from a process control circuit to the power reception circuit to receive the measurement data from the power reception circuit and supply the same to the process control circuit.