PURPOSE: To attain synchronization without provision of a central station with respect to the mutual automonous decentralized synchronization system between base stations in the communication network system comprising the plural base stations for mobile communication and lots of mobile stations such as an automatic telephone set or a portable telephone set.

CONSTITUTION: Phases of transmission signals of base stations A1-C3 are represented by θ1-θ3 and phase error signals are represented by Δθ1-Δθ3. The operation of phase correction by phase control sections 7-9 of the stations A1-C3 is the same, and in the case of,e.g. the station A1, a transmission signal from the stations B2, C3 is received and the phases θ2, θ3 are detected and they are compared with the phase θ1 of the transmission signal of its own station. Then the phases θ2-θ1 and θ3-θ1 as the result of comparison are averaged, an error signal Δθ1 is obtained and the phase correction from θ1+Δθ1 into θ1 in the transmission signal of its own station is implemented. The transmission signal of other station to be referenced may be not only from the base station but also from a mobile station in communication service areas 4-6 synchronously with the base station.