AIR CONDITIONER

Provided is an air conditioner that can provide information from which the root cause of an error can be estimated in the event of a fault without depending on the ability of the service personnel. An air conditioner (1) includes a controller (12) that controls operation of the air conditioner (1) on the basis of information from sensors (8) and operating information from devices (9, 10, 11) and that executes, for example, protection control, error detection, and abnormal shutdown thereof. The controller (12) includes a root-cause-of-fault-estimation-data acquiring section (13) that computes at least first to third most-frequent protection control factors and error detection factors among a plurality of preset protection control factors and error detection factors, that ranks and stores the factors, and that allows the stored information to be displayed when necessary.