A guided bone regeneration membrane has a bilayer structure including a first nonwoven fabric layer and a second nonwoven fabric layer. The first nonwoven fabric layer includes a fibrous substance containing a biodegradable resin as a principal component and further containing a siloxane, and the second nonwoven fabric layer includes a fibrous substance containing a biodegradable resin as a principal component. The first and second nonwoven fabric layers are electrospun nonwoven fabric layers, and the fibrous substance constituting the second nonwoven fabric layer has an average diameter smaller than that of the fibrous substance constituting the first nonwoven fabric layer. Specifically, the fibrous substance constituting the second nonwoven fabric layer preferably has an average diameter of more than 0 &mu；m and equal to or less than 5 &mu；m.
