A data transmission method and a data transmission device are disclosed. The method comprises: sending, by a transmitting end, a channel request frame to a first receiving end on at least two sub-channels; parsing, by a receiving end after receiving a channel response frame from the first receiving end, the channel response frame to obtain second channel indication information; determining that the sub-channel on which the channel response frame is transmitted is idle; and sending data to the first receiving end on the sub-channel that is determined to be idle.