An examination of relationships between the strength and performance of microneedles comprising a biodegradable resin and coated with a coating material revealed that microneedles comprising a biodegradable resin with given or higher strength, i.e., a given weight-average molecular weight, and coated with a coating material have excellent performance. With respect to coating materials also, a given kind and a given amount were found to be useful for making the microneedles exhibit the performance. A microneedle device (1) which comprises a microneedle array (2) composed of microneedles (3) comprising a polylactic acid having a weight-average molecular weight of 40,000 or higher, at least some of the array (2) having been coated with a support containing a physiologically active ingredient, enables the physiologically active ingredient to have excellent transferability to the living body.
