Provided is a synchronization establishment method capable of reducing the time required to establish synchronization in a slave station without putting an unnecessary load on a master station. In the synchronization establishment method, a one-second cycle of a message is divided into 100 time slots including slot “0” to slot “99”; ten slots including slot “90” to slot “99” as some of the slots are allocated to a fast synchronization establishment mode; and, in the fast synchronization establishment mode, messages such as Sync2, Delay_Req, and Delay_Resp are transmitted and received between the master station and the slave station so that the slave station establishes synchronization.