To provide an 'intelligent' air compressor capable of carrying out a self-diagnosis of a dangerous state existing in the compressor.

This device for monitoring a state of an air compressor is provided with a plurality of sensors 12, 14, 16 appropriately disposed so as to sensitize operation parameters 12a-12g, 14a-14e, 16a-16d of the air compressor and output a signal 18 representing respective states of the operation parameters. An information processing device 10 is connected to the sensors 12, 14, 16 such that it receives the output signal 18 from these sensors 12, 14, 16 and transmits output control signals 20, 22, 28 corresponding thereto. The output control signals 20, 22, 28 include an information capable of appropriately controlling and preparing the air compressor.