The invention relates to a transdermal microneedle unit and a transdermal microneedle drug delivery device including the transdermal microneedle unit. The transdermal microneedle unit includes a plurality of sheets stacked with each other, each sheet having at least one through hole defined thereon and a barbule arranged at the periphery of the through hole, wherein the through hole on one sheet is penetrated by the barbules of other sheets and the barbules being juxtaposed to form at least one triangular pyramidal transdermal microneedle. The transdermal microneedle drug delivery device comprises a substrate, a transdermal microneedle unit, a union joint and an injection syringe.
