Each of a first switching processor and a second switching processor included in a switching device switches plural pieces of data to determined destinations. A controller bypass-transmits a determined number of pieces of data received by the first switching processor to the second switching processor according to a congestion state of the first switching processor to make both of the first switching processor and the second switching processor perform a switching process. Alternatively, the controller bypass-transmits a determined number of pieces of data received by the second switching processor to the first switching processor according to a congestion state of the second switching processor to make both of the first switching processor and the second switching processor perform a switching process.