A monitoring apparatus for monitoring air-conditioning apparatuses, each air-conditioning apparatus being configured to perform air-conditioning of a target space and each air-conditioning apparatus including a refrigerant circuit in which refrigerant is circulated, the refrigerant circuit including at least a compressor, a heat source-side heat exchanger, an expansion device, and a use-side heat exchanger, the monitoring apparatus comprising: a storage device configured to store operation data received from air condition apparatuses and indicating an operation state of the air-conditioning apparatuses, the storage device is connected via an electrical communication line with the apparatuses; and a monitoring processing device configured to perform abnormality detection by extracting, from the storage device, past operation data of collected the air-conditioning apparatuses stored in the storage device and satisfying an extraction condition, the extraction condition including a kind of the refrigerant and a specification of a device included in the air-conditioning apparatus that is a target of monitoring by the monitoring apparatus, the extraction condition on the specification of the device having a predefined range within which the specification of the device is equated, and comparing the extracted operation data with operation data of the air-conditioning apparatus that is the target of monitoring, characterized in that the operation data is stored in the storage device to be associated with data on weather at a time when each of the air-conditioning apparatuses is operated, the monitoring processing device is configured to set at least one of rain or wind as a weather condition, and the monitoring processing device is configured to avoid using operation data to perform the abnormality detection, the operation data being associated with the data on weather not satisfying the set weather condition. a storage device configured to store operation data received from air condition apparatuses and indicating an operation state of the air-conditioning apparatuses, the storage device is connected via an electrical communication line with the apparatuses; and a monitoring processing device configured to perform abnormality detection by extracting, from the storage device, past operation data of collected the air-conditioning apparatuses stored in the storage device and satisfying an extraction condition, the extraction condition including a kind of the refrigerant and a specification of a device included in the air-conditioning apparatus that is a target of monitoring by the monitoring apparatus, the extraction condition on the specification of the device having a predefined range within which the specification of the device is equated, and comparing the extracted operation data with operation data of the air-conditioning apparatus that is the target of monitoring, characterized in that the operation data is stored in the storage device to be associated with data on weather at a time when each of the air-conditioning apparatuses is operated, the monitoring processing device is configured to set at least one of rain or wind as a weather condition, and the monitoring processing device is configured to avoid using operation data to perform the abnormality detection, the operation data being associated with the data on weather not satisfying the set weather condition.