A disposable diaper having a longitudinal direction and a transverse direction, comprising: a chassis including a skin-facing side, a non-skin-facing side, a front waist region, a rear waist region and a crotch region extending in the longitudinal direction between the front and rear waist regions; and a bodily fluid absorbent structure which comprises an absorbent core and at least one sheet covering a surface of the absorbent core; the bodily fluid absorbent structure extends in the longitudinal direction across the crotch region into the front and rear waist regions, wherein a region of the bodily fluid absorbent structure extending at least in a central area thereof is formed with a high stiffness region comprising a plurality of debosses spaced one from another in predetermined dimensions in the longitudinal and transverse directions, characterised in that: the debosses are respectively shaped so that the length dimension thereof in the transverse direction is longer than the length dimension thereof in the longitudinal direction; the high stiffness region is formed in an area of the crotch region biased toward the front waist region; the high stiffness region includes a plurality of longitudinal low stiffness zones extending in the longitudinal direction and formed with none of the debosses, a plurality of transverse high stiffness zones formed with the debosses arranged at regular intervals in the transverse direction, and transverse low stiffness zones each lying between each pair of the transverse high stiffness zones and formed with none of the debosses; the transverse low stiffness zones and transverse high stiffness zones are adjacent in the longitudinal direction; in the high stiffness region, the width dimension of the transverse low stiffness zones in the longitudinal direction is larger than the width dimension of the longitudinal low stiffness zones in the transverse direction; and the debosses are arranged in a zigzag-pattern on the skin-facing side or on the non-skin-facing side, or on both the skin-facing and non-skin-facing sides of the bodily fluid absorbent structure. a chassis including a skin-facing side, a non-skin-facing side, a front waist region, a rear waist region and a crotch region extending in the longitudinal direction between the front and rear waist regions; and a bodily fluid absorbent structure which comprises an absorbent core and at least one sheet covering a surface of the absorbent core; the bodily fluid absorbent structure extends in the longitudinal direction across the crotch region into the front and rear waist regions, wherein a region of the bodily fluid absorbent structure extending at least in a central area thereof is formed with a high stiffness region comprising a plurality of debosses spaced one from another in predetermined dimensions in the longitudinal and transverse directions, characterised in that: the debosses are respectively shaped so that the length dimension thereof in the transverse direction is longer than the length dimension thereof in the longitudinal direction; the high stiffness region is formed in an area of the crotch region biased toward the front waist region; the high stiffness region includes a plurality of longitudinal low stiffness zones extending in the longitudinal direction and formed with none of the debosses, a plurality of transverse high stiffness zones formed with the debosses arranged at regular intervals in the transverse direction, and transverse low stiffness zones each lying between each pair of the transverse high stiffness zones and formed with none of the debosses; the transverse low stiffness zones and transverse high stiffness zones are adjacent in the longitudinal direction; in the high stiffness region, the width dimension of the transverse low stiffness zones in the longitudinal direction is larger than the width dimension of the longitudinal low stiffness zones in the transverse direction; and the debosses are arranged in a zigzag-pattern on the skin-facing side or on the non-skin-facing side, or on both the skin-facing and non-skin-facing sides of the bodily fluid absorbent structure. the debosses are respectively shaped so that the length dimension thereof in the transverse direction is longer than the length dimension thereof in the longitudinal direction; the high stiffness region is formed in an area of the crotch region biased toward the front waist region; the high stiffness region includes a plurality of longitudinal low stiffness zones extending in the longitudinal direction and formed with none of the debosses, a plurality of transverse high stiffness zones formed with the debosses arranged at regular intervals in the transverse direction, and transverse low stiffness zones each lying between each pair of the transverse high stiffness zones and formed with none of the debosses; the transverse low stiffness zones and transverse high stiffness zones are adjacent in the longitudinal direction; in the high stiffness region, the width dimension of the transverse low stiffness zones in the longitudinal direction is larger than the width dimension of the longitudinal low stiffness zones in the transverse direction; and the debosses are arranged in a zigzag-pattern on the skin-facing side or on the non-skin-facing side, or on both the skin-facing and non-skin-facing sides of the bodily fluid absorbent structure.