A disposable diaper, comprising: a liquid-permeable topsheet; a backsheet; an absorber (40G, 40H, 40J) arranged between the topsheet and the backsheet and having a front-back direction extending toward foreside and rearside of a wearer and a widthwise direction orthogonal to the front-back direction; an urination region which is a region in contact with an urination portion of the wearer; a buttocks region which is arranged to the rear of the urination region and is a region in contact with buttocks of the wearer; a ventral region which is arranged to the front of the urination region and is a region in contact with the ventral of the wearer, and exterior sheets which constitute the exterior portion of the disposable diaper, wherein a front waistband edge, positioned on the outside of the ventral region in a widthwise direction of the disposable diaper, is joined to a rear waistband edge, positioned on the outside of the buttocks region in the widthwise direction, whereby the disposable diaper is formed into the pants-type, the absorber (40G, 40H, 40J) has a first region including absorbent polymer and a second region in which absorbent polymer has a lower basis weight than that in the first region; the first region is only provided in the absorber of the ventral region; the second region is arranged in the absorber of the urination region; and a deformation restraining unit is formed to be capable of restraining deformation of the urination region from being propagated to the first region in the inner side in the front-back direction with respect to the inner end in the front-back direction of the first region, wherein the deformation restraining unit is configured by at least any one of: a constriction portion that a side portion of the absorber is constricted inward in the widthwise direction; a slit formed in the absorber; a low basis weight region, in the absorber, that has a lower basis weight than that of the surrounding; a compressed portion in which the absorber is compressed in a thickness direction; a widthwise stretch member that stretches in the widthwise direction; and a difference in rigidity of the absorber. a liquid-permeable topsheet; a backsheet; an absorber (40G, 40H, 40J) arranged between the topsheet and the backsheet and having a front-back direction extending toward foreside and rearside of a wearer and a widthwise direction orthogonal to the front-back direction; an urination region which is a region in contact with an urination portion of the wearer; a buttocks region which is arranged to the rear of the urination region and is a region in contact with buttocks of the wearer; a ventral region which is arranged to the front of the urination region and is a region in contact with the ventral of the wearer, and exterior sheets which constitute the exterior portion of the disposable diaper, wherein a front waistband edge, positioned on the outside of the ventral region in a widthwise direction of the disposable diaper, is joined to a rear waistband edge, positioned on the outside of the buttocks region in the widthwise direction, whereby the disposable diaper is formed into the pants-type, the absorber (40G, 40H, 40J) has a first region including absorbent polymer and a second region in which absorbent polymer has a lower basis weight than that in the first region; the first region is only provided in the absorber of the ventral region; the second region is arranged in the absorber of the urination region; and a deformation restraining unit is formed to be capable of restraining deformation of the urination region from being propagated to the first region in the inner side in the front-back direction with respect to the inner end in the front-back direction of the first region, wherein the deformation restraining unit is configured by at least any one of: a constriction portion that a side portion of the absorber is constricted inward in the widthwise direction; a slit formed in the absorber; a low basis weight region, in the absorber, that has a lower basis weight than that of the surrounding; a compressed portion in which the absorber is compressed in a thickness direction; a widthwise stretch member that stretches in the widthwise direction; and a difference in rigidity of the absorber.