An outer bag for disposable body warmer packaging and a disposable body warmer are provided that are excellent in a gas barrier property that inhibits permeation of oxygen gas, water vapor, and the like, which can allow swelling due to hydrogen gas generated during a storage period to be prevented.Provided is an outer bag for disposable body warmer packaging having an accommodating portion accommodating a disposable body warmer accommodated in an air-permeable inner bag and generating heat through contact with air, the outer bag comprising a low air-permeability portion having an oxygen permeability of 1.5 to 20 cc/m2·day·atm measured at 20° C. and 90% RH and having a water vapor permeability of 0.05 to 10 g/m2·day measured at 40° C. and 90% RH; and an air-impermeable portion having an oxygen permeability of 1.3 cc/m2·day·atm or lower measured at 20° C. and 90% RH and a water vapor permeability of 2.0 g/m2·day or lower measured at 40° C. and 90% RH, wherein a ratio of an area of the low air-permeability portion to a total internal area of the accommodating portion is 15 to 75%.