A method for relaying received data by a relay node in a sensor network that includes a sink node, a source node for collecting and transmitting data requested by the sink node, and the relay node for relaying the data transmitted from the source node to the sink node. The relay node determines whether the source node that transmits the data is a previously identified source node, stores the data in a buffer and forwards the data to a neighbor node when the source node transmitting the data is the previously identified source node according to the determination. The data is managed based on the relay node having the buffer, rather than the source node and the sink node as in the related art. Further, the data error can be promptly handled.