A base station apparatus used in a communication system having a time division communication scheme in which a plurality of base station apparatuses are connected and synchronize with reference to a master base station apparatus, the base station apparatus comprising: a processor, adapted to: for each of all pairs of two communicable base station apparatuses, collect parameters concerning received electric field strength of communications between the two communicable base station apparatuses, the received electric field strength being measured by each of the plurality of base station apparatuses; select each of the plurality of base station apparatuses as a candidate base station apparatus, and for each of the candidate base station apparatuses - compare the collected parameters to set a route communicable directly or indirectly through one or more other interposed base station apparatuses between the candidate base station apparatuses and each one of all the other base station apparatuses other than the candidate base station apparatuses among the plurality of base station apparatuses; and - check the number of the interposed base station apparatus(es) in each route to determine the maximum number of interposing among the routes as set; and select a candidate base station apparatus which has the smallest maximum number of interposing among the candidate base station apparatuses and decide the selected candidate base station as the master base station apparatus. a processor, adapted to: for each of all pairs of two communicable base station apparatuses, collect parameters concerning received electric field strength of communications between the two communicable base station apparatuses, the received electric field strength being measured by each of the plurality of base station apparatuses; select each of the plurality of base station apparatuses as a candidate base station apparatus, and for each of the candidate base station apparatuses - compare the collected parameters to set a route communicable directly or indirectly through one or more other interposed base station apparatuses between the candidate base station apparatuses and each one of all the other base station apparatuses other than the candidate base station apparatuses among the plurality of base station apparatuses; and - check the number of the interposed base station apparatus(es) in each route to determine the maximum number of interposing among the routes as set; and select a candidate base station apparatus which has the smallest maximum number of interposing among the candidate base station apparatuses and decide the selected candidate base station as the master base station apparatus. for each of all pairs of two communicable base station apparatuses, collect parameters concerning received electric field strength of communications between the two communicable base station apparatuses, the received electric field strength being measured by each of the plurality of base station apparatuses; select each of the plurality of base station apparatuses as a candidate base station apparatus, and for each of the candidate base station apparatuses - compare the collected parameters to set a route communicable directly or indirectly through one or more other interposed base station apparatuses between the candidate base station apparatuses and each one of all the other base station apparatuses other than the candidate base station apparatuses among the plurality of base station apparatuses; and - check the number of the interposed base station apparatus(es) in each route to determine the maximum number of interposing among the routes as set; and - compare the collected parameters to set a route communicable directly or indirectly through one or more other interposed base station apparatuses between the candidate base station apparatuses and each one of all the other base station apparatuses other than the candidate base station apparatuses among the plurality of base station apparatuses; and - check the number of the interposed base station apparatus(es) in each route to determine the maximum number of interposing among the routes as set; and select a candidate base station apparatus which has the smallest maximum number of interposing among the candidate base station apparatuses and decide the selected candidate base station as the master base station apparatus.