Provided is a method, performed by a cordless vacuum cleaner, of automatically adjusting the strength of a suction power of a suction motor. More specifically, the method may include obtaining data about a flow path pressure measured by a pressure sensor, obtaining data related to a load of the brush apparatus through a load detection sensor, identifying a current usage environment state of the brush apparatus by applying the data related to the flow path pressure and the data related to the load of the brush apparatus to an AI model stored in a memory of the cordless vacuum cleaner, and adjusting the strength of the suction power of the suction motor, based on the identified current usage environment state of the brush apparatus.