Provided are a compressor and a monitoring system that can specify a cause of an anomaly of a sensed value of a sensor. A compressor (1) includes: a temperature sensor (11A) that senses a temperature of a compressed air on a discharge side of a low-pressure-stage compressor body (3) and on an upstream side of an intercooler (5); a pressure sensor (12A) that senses a pressure of the compressed air on the discharge side of the low-pressure-stage compressor body (3); a temperature sensor (11B) that senses a temperature of the compressed air on an intake side of a high-pressure-stage compressor body (6) and on a downstream side of the intercooler (5); a temperature sensor (11C) that senses a temperature of the compressed air on a discharge side of the high-pressure-stage compressor body (6); a controller (8) that decides whether or not an anomaly has occurred in sensed values of the sensors (11A), (11B), (11C), and (12A), and estimates a cause of the anomaly; and a display device (9) that displays the cause of the anomaly estimated by the controller (8).