A disposable diaper having a longitudinal direction and a transverse direction, comprising a side facing the wearer's skin and a side facing away from the wearer's skin, a front waist region, a rear waist region, a crotch region extending between said front and rear waist regions (13, 14), a waist-opening, a pair of leg-openings (17a, 17b), an elastic front waist panel defining said front waist region, an elastic rear waist panel defining said rear waist region and a liquid-absorbent chassis containing a liquid-absorbent core, said disposable diaper being characterized in that: said front and rear waist panels (18, 19) respectively include an inner sheet (20, 21) formed of an elastic sheets and lying on said side facing the wearer's skin and an outer sheet (22, 23) having a trapezoidal shape and bonded to at least said side of said inner sheet (20, 21) facing away from the wearer's skin; front and rear ends portions of said liquid-absorbent chassis are respectively sandwiched between the inner sheet (20, 21) having a rectangular shape and the outer sheet (22, 23) and attached at least to the inner sheet (20, 21); the elastic sheet defining the inner sheet (20, 21) includes an elastic nonwoven fabric disposed on the side facing the wearer's skin and an inelastic nonwoven fabric disposed on the side facing away from the wearer's skin and the elastic nonwoven fabric is bonded under tension to said inelastic nonwoven fabric; at least in said rear waist region of said front and rear waist regions (13, 14), a portion of said elastic nonwoven fabric corresponding to an end portion of said liquid-absorbent core is partially formed with a low elasticity zone (30a, 30b) having a lower tensile stress than in a remaining region of the elastic nonwoven fabric; the low elasticity zone (30a, 30b) of the inner sheet (20, 21) is formed by cutting the elastic nonwoven fabric by a plurality of slits each extending in the longitudinal direction and arranged in a staggered pattern; the outer sheet (22, 23) includes an inelastic nonwoven fabric and a plurality of strand-like elastic elements (32, 35, 37) extending in the transverse direction and attached to the inelastic nonwoven fabric under tension; a portion of the outer sheet (22, 23) corresponding to both a front and a rear end portion of the liquid-absorbent core is formed with an inelastic zone (34, 36); and the inelastic zone (34, 36) of the outer sheet (22, 23) is formed by partially cutting or removing the elastic elements (32, 35, 37). said front and rear waist panels (18, 19) respectively include an inner sheet (20, 21) formed of an elastic sheets and lying on said side facing the wearer's skin and an outer sheet (22, 23) having a trapezoidal shape and bonded to at least said side of said inner sheet (20, 21) facing away from the wearer's skin; front and rear ends portions of said liquid-absorbent chassis are respectively sandwiched between the inner sheet (20, 21) having a rectangular shape and the outer sheet (22, 23) and attached at least to the inner sheet (20, 21); the elastic sheet defining the inner sheet (20, 21) includes an elastic nonwoven fabric disposed on the side facing the wearer's skin and an inelastic nonwoven fabric disposed on the side facing away from the wearer's skin and the elastic nonwoven fabric is bonded under tension to said inelastic nonwoven fabric; at least in said rear waist region of said front and rear waist regions (13, 14), a portion of said elastic nonwoven fabric corresponding to an end portion of said liquid-absorbent core is partially formed with a low elasticity zone (30a, 30b) having a lower tensile stress than in a remaining region of the elastic nonwoven fabric; the low elasticity zone (30a, 30b) of the inner sheet (20, 21) is formed by cutting the elastic nonwoven fabric by a plurality of slits each extending in the longitudinal direction and arranged in a staggered pattern; the outer sheet (22, 23) includes an inelastic nonwoven fabric and a plurality of strand-like elastic elements (32, 35, 37) extending in the transverse direction and attached to the inelastic nonwoven fabric under tension; a portion of the outer sheet (22, 23) corresponding to both a front and a rear end portion of the liquid-absorbent core is formed with an inelastic zone (34, 36); and the inelastic zone (34, 36) of the outer sheet (22, 23) is formed by partially cutting or removing the elastic elements (32, 35, 37).