The invention discloses an air compressor. The air compressor comprises a crankcase, two high-pressure cylinder assemblies, two low-pressure cylinder assemblies and a motor, wherein a crankshaft assembly is arranged in the crankcase, the two high-pressure cylinder assemblies are correspondingly arranged on the two sides of the crankcase and connected to the crankshaft assembly, the two low-pressure cylinder assemblies are correspondingly arranged on the two sides of the crankcase and connected to the crankshaft assembly, the motor is connected to the crankshaft assembly through an elastic coupler, after the motor is started and drives the crankshaft assembly to rotate through the elastic coupler, sucked environment air is subjected to first-stage compression through the low-pressure cylinder assemblies, and the environment air subjected to first-stage compression enters an intercooler to be cooled, the high-pressure cylinder assemblies are used for carrying out second-stage compression on the environment air subjected to first-stage compression and cooling, the environment air subjected to second-stage compression enters an aftercooler to be cooled, and finally compressed air is output. According to the air compressor, a buffer chamber is arranged in front of the crankcase, so that the air suction buffer volume is further increased, and the air suction noise is reduced.