The present invention relates to a backing for a water-based patch consisting of the following constituents, wherein the backing is excellent in pasty preparation retention and moisture retention, improves the persistence of drug efficacy by inhibiting the sublimation of the drug, gives neither restrained feeling nor rough feeling due to a thin thickness and an excellent elasticity, controls the moisture permeability, gives almost no sticky feeling and thereby gives an excellent feeling in application. A patch backing for a water-based pasty preparation consisting of a laminate, wherein the laminate consists of three layers, a film layer having through-holes is laminated between a nonwoven fabric layer A and a nonwoven fabric layer B, said film layer consists of a resin containing an olefin elastomer, the through-hole area per a hole is 0.02-0.18 mm2, and the opening ratio of the through-hole is 1-10%.