An applicator is configured to transfer an active ingredient into a body through skin by a puncture in the skin with microneedles. The applicator includes a piston plate that is provided with a first protrusion part and second protrusion parts on a lower surface side of a main body of the piston plate. The microneedles are provided on a surface of the first protrusion part. The second protrusion parts are provided in a periphery of the first protrusion part while spaced apart from the first protrusion part.