The objective of the present invention is to effectively administer an active ingredient without making a user nervous when applying microneedles. An applicator (10) is provided with a transmission member which transmits a biasing force of a bias member to a microneedle array (90) which has microprojections (microneedles) with a needle density of 500 per cm2 or more. The mass of the transmission member is 1.5 g or less, and the momentum of the transmission member operated by the biasing force of the bias member is 0.0083-0.015 (Ns).本發明的目的，是在施用微型針時，不會給與利用者恐懼感而能夠有效率地施打活性成分。微型針施作器(10)，係具備傳達構件，該傳達構件可對具有針密度為500根/cm2以上之微小突起(微型針)的微型針陣列(90)傳遞彈推構件的彈推力。傳達構件的質量為1.5g以下，藉由彈推構件的彈推力而動作之傳達構件的運動量為0.0083(Ns)以上、0.015(Ns)以下。
