Needle assembly for transdermal administration and method for manufacturing same

A needle assembly for transdermal administration that comprises a substrate provided with a first surface and a second surface opposite to the first surface, and a plurality of microneedles projecting perpendicularly to the first surface. In the substrate, a plurality of grooves are positioned in the first surface and/or the second surface. The needle assembly is configured so that the grooves deform the substrate following up the skin surface shape of a living body and, as a result, the axis of each microneedle is displaced toward the same direction as the normal line on the skin surface of the living body.