An underpants-type disposable diaper is of a size and a water absorption capacity suitable for infants 3 to 6 years old, and is capable of preventing the protrusion of the groin portion of the diaper in use so that leakage does not occur. The leakage can be avoided by increasing the size and the water absorption capacity of the diaper main body to a level suitable for infants 3 to 6 year olds still using diaper and at the same time improving the tracks of a plurality of elastic members disposed along the peripheral edges of leg holes so as to reduce the elasticity in the vertical direction of the crotch section and prevent the protrusion of an infants groin.
