PURPOSE: To utilize an under floor as a radiocommunication zone for safely and surely transmitting/receiving information signals between information processing devices indoors, and perform base isolation by means of a floor construction by which earthquake force is turned way as a countermeasure of earthquake.

CONSTITUTION: This double flooring system is constituted so that floor boards 10 respectively having leg bolts 20 adjustable their height on the four corners are arranged, or a bottom plate 6 and a receiving plate 8 are connected together through a post screw 9, the bottom plate 6 is provided on a bed floor 1, corners of four mortar floor boards 10 are placed on the receiving plate 8 and connected together. Transmitting devices and receiving devices of electric wave, ultrasonic wave, infrared rays, and light of high intensity under the floor are connected to electronic devices on the floor, and signals are transmitted and received in the space under the floor by the use of respective carrier waves.