CONSTRUCTION MACHINE WITH DEVICE FOR ACOUSTICALLY INSULATING CABIN

To be provided is a construction machine capable of effectively reducing noise which would intrude into a cab, without deterioration in ride quality, comfort and air-conditioning efficiency in the cab. The construction machine comprises a lower propelling body, an upper slewing body including an upper frame, a cab including a floor plate and installed on the upper frame, and a cab noise reduction device. The cab noise reduction device comprises: the floor plate; an under-cab member including a cab deck (11) supporting the cab and provided under the cab to define a closed-form under-cab space whose periphery is substantially closed, in cooperation with the floor plate; and a resonator (21) reducing noise in the under-cab space by a resonance effect.