The laundry processing device according to the present invention comprises: a first washing unit for doing laundry; and a second washing unit having a washing space independent from the first washing unit and provided with a tub of a smaller capacity than the first washing unit, wherein the first washing unit comprises: a first display unit; a first laundry amount detecting unit for measuring the amount of laundry in the first washing unit; and a first control unit for displaying, on the first display unit, a guide message recommending use of the second washing unit if the amount of laundry measured by the first laundry amount detecting unit is less than a first set value. When the amount of laundry is relatively small, the user is induced to use the second washing unit, thereby reducing power consumption.