A method for controlling a laundry processing apparatus according to an embodiment of the present disclosure comprises steps of: inputting power to at least a second processing device and, through an input unit in the second processing device, inputting an installation inspection instruction for the second processing device; performing a primary inspection process by the installation inspection instruction; and performing a second inspection process after the primary inspection process is completed. In the primary inspection process, the control unit of the second processing device controls a plurality of inspections to proceed automatically in sequence, and the plurality of inspections may comprise at least two of a pairing inspection, a drawer closing state inspection, a drawer locking state inspection, and a lid closing state inspection.