A multilayer nanofiber sheet comprising: a nanofiber layer including nanofibers having a thickness of from 10 to 3000 nm in terms of equivalent circle diameter (measured via SEM under conditions as pointed out in the description) and which comprise a water-soluble polymer compound; a substrate layer arranged on one surface side of the nanofiber layer; and a water-insoluble porous layer arranged on the other surface side of the nanofiber layer, wherein: the three layers are layered; and the multilayer nanofiber sheet is configured to be used in a state in which a surface thereof on the porous layer side is arranged so as to face a surface of an object wherein the water-soluble polymer compound has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the polymer compound is immersed in 10 g of ion-exchanged water, at least 0.5 g of the immersed polymer compound dissolves into water after 24 hours; and wherein the water-insoluble porous layer has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the porous layer is immersed in 10 g of ion-exchanged water, more than 0.5 g of the immersed porous layer remains undissolved in water after 24 hours. a nanofiber layer including nanofibers having a thickness of from 10 to 3000 nm in terms of equivalent circle diameter (measured via SEM under conditions as pointed out in the description) and which comprise a water-soluble polymer compound; a substrate layer arranged on one surface side of the nanofiber layer; and a water-insoluble porous layer arranged on the other surface side of the nanofiber layer, wherein: the three layers are layered; and the multilayer nanofiber sheet is configured to be used in a state in which a surface thereof on the porous layer side is arranged so as to face a surface of an object wherein the water-soluble polymer compound has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the polymer compound is immersed in 10 g of ion-exchanged water, at least 0.5 g of the immersed polymer compound dissolves into water after 24 hours; and wherein the water-insoluble porous layer has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the porous layer is immersed in 10 g of ion-exchanged water, more than 0.5 g of the immersed porous layer remains undissolved in water after 24 hours. the three layers are layered; and the multilayer nanofiber sheet is configured to be used in a state in which a surface thereof on the porous layer side is arranged so as to face a surface of an object wherein the water-soluble polymer compound has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the polymer compound is immersed in 10 g of ion-exchanged water, at least 0.5 g of the immersed polymer compound dissolves into water after 24 hours; and wherein the water-insoluble porous layer has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the porous layer is immersed in 10 g of ion-exchanged water, more than 0.5 g of the immersed porous layer remains undissolved in water after 24 hours. wherein the water-soluble polymer compound has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the polymer compound is immersed in 10 g of ion-exchanged water, at least 0.5 g of the immersed polymer compound dissolves into water after 24 hours; and wherein the water-insoluble porous layer has a property wherein, in an environment of 1 atm. and 23 °C, when 1 g of the porous layer is immersed in 10 g of ion-exchanged water, more than 0.5 g of the immersed porous layer remains undissolved in water after 24 hours. <EOS>