To provide a water-degradable sheet capable of preventing, through biodegradation, drainage apparatuses such as septic tanks from clogging and capable of achieving both water resistance and water solubility, and a pouch for an excretion receptacle including the same, there is provided a a water-degradable sheet capable of dissolving in water when dipped in water, where the water-degradable sheet contains an enzyme to decompose the water-degradable sheet thereinside and the substrate of the water-degradable sheet includes a water-degradable paper layer and a water-resistant layer. Preferably, the water-resistant layer includes a biodegradable substrate.