An active agent is effectively administered without giving fear to the user when the microneedles are applied. An applicator 10 includes a transmission member that transmits biasing force of a biasing member to a microneedle array including micro projections (microneedles) with a needle density of 500 needles/cm2 or more. The transmission member has a mass of 1.5 g or less, and the transmission member activated by the biasing force of the biasing member has a momentum of from 0.0083 (N·s) to 0.015 (N·s).
