In order to measure time correlation of primary cosmic rays, a network obse
rvation of extensive air showers started in Japan. The network as Large Are
a Air Shower (LAAS) group consists of nine air-shower-stations (seven insti
tutes and 26,000 km(2)) using the Global Positioning system (GPS). We propo
se an analytical procedure to extract time-limited fractal structure from t
ime series of arrival time intervals of successive air showers and present
the results of the analysis by using the network data.