A disposable diaper includes a liquid-pervious topsheet, a liquid-impervious backsheet, a liquid-absorbent core interposed between these top- and backsheets, and an indicator by which it is perceptible from outside the backsheet whether urination has occurred or not. The indicator has a liquid-pervious intermediate sheet hydrophilically modified by coating of a hydrophobic fibrous nonwoven fabric with surfactant and a water-soluble coloring agent depicting a given figure which is perceptible from outside the backsheet. The intermediate sheet is interposed between the backsheet and the core and the coloring agent is applied on the surface of the intermediate sheet opposed to the backsheet.