Abstract: A sound amplification structure includes a sound path that is formed by an underfloor foundation of a building and a concrete peripheral wall formed by standing up approximately vertically from the underfloor foundation. One end of the sound path (a speaker unit communication section) is able to communicate with a floor speaker unit placed in a room of the building. A width of the sound path widens from the one end toward other end of the sound path. The other end of the sound path (an output unit) is able to output sounds that are emitted from the floor speaker unit and amplified through the sound path. A length of the sound path is 4 m or longer. Preferably, the sound path is U-shaped, Z-shaped, or a zig-zag shaped. The concrete peripheral wall preferably doubles as a building foundation structure.