A laundry machine includes first and second washing units including first and second tubs, respectively. First and second drums are mounted inside the first and second tubs, and first and second drive units drive rotations of the first and second drums around first and second rotational shafts, respectively. The second washing unit is arranged above the first washing unit and has a smaller laundry treating capacity than the first washing unit. The first rotational shaft is not parallel to the second rotational shaft. A first recess projects downward from a rear lower surface of the second tub and is configured to heat wash water in the second tub. A metal plate member is provided on an outside lower surface of the second tub, and partially extends to the rear of the second tub to expose a bottom surface of the first recess.