A noise reduction structure includes a compressor discharge-side pipe portion, a first porous plate having a plurality of through holes and extending circumferentially along an inner circumferential surface of the compressor discharge-side pipe portion so that an air layer is formed between the first porous plate and the inner circumferential surface, a partition dividing an interior of the compressor discharge-side pipe portion in a radial direction in a circumferential direction of the compressor discharge-side pipe portion so as to form a plurality of flow paths in the compressor discharge-side pipe portion, and a second porous plate having a plurality of through holes. The second porous plate is provided in each of the plurality of flow paths and extends along the partition so that an air layer is formed between the second porous plate and the partition.