The present invention relates to a laundry processing apparatus and a control method therefor, and to a laundry processing apparatus having a plurality of washing parts for performing washing independently of each other, the apparatus: determining whether the plurality of washing parts simultaneously perform washing; and determining whether a simultaneous operation is performed on the basis of the time required when water is supplied, so as to determine an error for the simultaneous operation on the basis of a standard different from an error determination standard during a single operation, thereby reducing the errors frequently occurring because of the simultaneous operation in a normal state.