A handheld air purifier may include a suction body provided with a fan to suction air and a filter to filter foreign matter from the sucked air, a handle extending from the suction body, and an agitator provided in the suction body to loosen or scatter dust from a garment. The handheld air purifier may be configured to be attached to and detached from a main air purifier, and the main air purifier may suction dust off the handheld air purifier and sterilize the handheld air purifier when the handheld air purifier is mounted on the main air purifier. The agitator of the handheld air purifier may have a striking member exposed through a lower surface of the suction body, and may move out of and into the suction body to strike the garment so that the dust may be loosened and suctioned into the suction body and filtered by the filter.