An air conditioner and a method for detecting an incorrectly connected pipe in an air conditioner are provided. The air conditioner may detect an incorrectly connected pipe by performing a serial pipe inspection when three or less indoor units are connected to an outdoor unit through pipes and performing a group pipe inspection when four or more indoor units are connected to the outdoor unit through the pipes. The structure may enable detecting the incorrectly connected pipe among pipes connecting the outdoor unit to the indoor units within a shorter time.