An operation method of a first communication node among a plurality of communication nodes included in an Ethernet-based vehicle network may include steps of measuring a first link delay for performing time synchronization with a second communication node included in the plurality of communication nodes; calculating a difference between the first link delay and an average value of a plurality of link delays measured before the measurement of the first link delay; comparing the calculated difference with a first threshold value for controlling a link delay measurement cycle for the second communication node; and controlling the link delay measurement cycle for the second communication node based on the comparison result.