The fundamental and serious problem of solar desalination, one of the most promising technique to solve the global water shortage, is poor efficiency. To improve the solar-to-vapor efficiency, a new device based on three-dimensional graphene networks (3DGNs) with a high solar absorption property and a mesoporous structure has been developed. The device contains 3DGN-photoabsorbers and a wood post that serves to deliver water and prevent heat loss to bulk water by a capillary force and thermal insulation property, respectively. It has shown greatly enhanced solar-to-vapor conversion efficiency of about 91.8% under one sun illumination and excellent desalination efficiency of five orders salinity decrement. Since this highly efficient solar desalination device is made by mass-producible 3DGNs and the earth-abundant wood piece, it provides a straightforward way to efficiently supply worldwide clean water.