A perforated soundproof structure is formed by oppositely arranging an external plate 1 and an internal plate 2 having a number of through-holes 2a. The board thickness, hole diameter and open area ratio of the internal plate 2 are set to satisfy design conditions to give rise to a viscous effect in the air passing through the through-holes 2a, and the design conditions are set so that the frequency bandwidth to attain an absorption coefficient of 0.3 or more is 10% or more of the resonance frequency.