Provided are a method of applying a microneedle array, and a patch or an assistant tool used therefor. When skin is to be stretched and punctured with microneedles, the microneedle array can be prevented from detaching from the skin by providing adhesive layers, with the microneedle array therebetween, in a direction different from the direction in which the skin is stretched. Additionally, the application method can be appropriately implemented by producing a patch or an assistant tool having a rigid flat plate. As a result, the microneedle array can be punctured more accurately with less stress.