To provide an air compressor apparatus which keeps noise and vibration as low as possible when the compressor is being operated by improving sound insulation and vibration isolation so that a burden can be alleviated for a patient who receives medical treatment for respiratory insufficiency using the apparatus.

In an air compressor provided with a cooling chamber 24 and a compression chamber 25 in a vertically divided casing 21, the compression chamber 25 is made in the dual-box structure that a placing plate 31 is suspended by coil springs 32a to 32d in an inner box 26, and that a compressor 30 is placed on this placing plate 31 for suspended support.