A high-speed Ethernet apparatus having a multiple lane configuration and method for selectively operating the multiple lanes to allow lanes to participate or not in data transmission and reception. The Ethernet apparatus includes: a transfer rate control unit to set a state of each of multiple physical coding sub-layer (PCS) lanes inside to be the same as a state of corresponding each of multiple physical transmission lanes based on state change information that indicates whether the each physical transmission lane is activated or not, and to remove idle blocks from data blocks which are received at a transfer rate of a physical transmission lane in active state among the multiple physical transmission lanes; and a block allocating unit to allocate the data blocks from which the idle blocks have been removed through PCS lanes in active state that correspond to the physical transmission lanes in active state.