PURPOSE: To obtain an excellent sound-proof barrier against a high frequency by filling an intermediate part of two pieces of plates which have been brought to vibration insulation with a sound absorbing use fiber.

CONSTITUTION: To one GFRP (glass fiber reinforced plastic) plate 1' of two piece of GFRP plates 1, 1', a paper honeycomb material 2 is stuck, the other GFRP plate 1 is placed as it is on the paper honeycomb material 2 by leaving a space l, and while rolling in the paper honeycomb material 2 in only the peripheral part, the upper and the lower GFRP plates 1, 1' are stuck. In such a way, since the title barrier is formed by a structure consisting of two pieces of plates which have been brought to vibration insulation and the hollow part becomes elastic, the sound-proof performance becomes larger against a high frequency exceeding a resonance frequency of the hollow part.