Provided are a gateway apparatus for providing multi-channel functionality in a sensor network, and a method and an apparatus for interfacing using serial peripheral interface (SPI) in the gateway apparatus. The SPI interfacing apparatus is connected to a plurality of wireless transmit/receive units, and receives a data frame via an SPI to output the data frame to a wireless transmit/receive unit, based on information regarding selection of the wireless transmit/receive unit, wherein the information is contained in the data frame. Then, the SPI interfacing unit receives data frames from the wireless transmit/receive units to output the data frames in a predetermined order via an SPI. Thus, the wireless transmit/receive units for providing multi-channel functionality can interface a signal processing unit by using an SPI method.