To prevent the entering of water from the outside of a plate material, and surely fix the plate material on an enclosure of a building.

This invention relates to a nail fixing a wall underlayer material (plate material) 13 on the enclosure 24 of the building and a wall underlayer fixing structure using the same. A sealant 10 is adhered on the outer surface of the nail 1 from a head lower surface 4 over a neck 5. Driving resistance is low enough to easily drive the nail 1 when the nail 1 is driven into the surface of the wall underlayer material 13. Moreover, the sealant 10 is pushed out into a gap between the head lower surface 4 of the nail and the wall underlayer material 13 by driving the nail 1 and the sealant 10 of an appropriate quantity is put therebetween.