A network relay apparatus which conducts data transfer by using a plurality of network LSIs includes a transfer engine unit having at least two network LSIs and a central control unit which controls the operation state of the network relay apparatus. The transfer engine unit includes the network LSIs capable of changing over at least one of a clock and an operation which differ every function block, a load judgment unit for judging a load laid upon each of function blocks in the network LSI, and a frequency voltage control unit for individually changing over at least one of the clock and operation voltage supplied to each function block on the basis of the load judged by the load judgment unit.