Provided is a method of producing a microneedle array unit which is capable of suppressing damage to a microneedle array. The method of producing a microneedle array unit, including an array preparing step of preparing a microneedle array which includes a sheet and a plurality of needles arranged on one surface of the sheet; a container preparing step of preparing a container which includes an accommodating portion defining an opening and a space for accommodating the microneedle array, and a deformable portion disposed on a side opposite to the opening and integrated with the accommodating portion; an accommodating step of accommodating the microneedle array in the accommodating portion of the container by allowing the other surface of the sheet of the microneedle array and the deformable portion of the container to oppose each other; and a deforming step of deforming an outer surface of the accommodating portion inward, which is positioned between the one surface of the sheet of the microneedle array and the opening of the accommodating portion, to form a protrusion that reduces an area of the opening.