The present invention provides a signal transmission method and device. The device includes: a transmitting device, configured to transmit a first signal to an opposite terminal; and a receiving device, configured to receive a second signal transmitted by the opposite terminal, where a frequency of the first signal is different from a frequency of the second signal, and the frequency of the first signal and/or the frequency of the second signal are/is in a frequency band of visible light. The present invention resolves a problem in a related technology that poor reliability of uplink and downlink signal transmission is caused when signals of a same frequency are used for uplink and downlink transmission, and provides a beneficial effect of improving reliability of uplink and downlink signal transmission.