A sound increase apparatus includes a first hollow body member that communicates with an intake flow path of an internal combustion engine, a second hollow body member that communicates with the first hollow body member, and a vibration member capable of vibrating in an out-of-plane direction, which is inserted in a connection between the first and second hollow body members and closes a cross section of the connection. The second hollow body member has a plurality of opening portions, each of which communicates with the air.