The present invention provides a drug delivery system by noninvasive administration, which is excellent in drug transfer to a tissue of the posterior segment of the eye via a local eye tissue. By administering a solid composition comprising a drug and a mucoadhesive substance having an adhesion strength of from 200 to 1000 g in the conjunctival sac, a drug delivery system excellent in drug transfer to a tissue of the posterior segment of the eye via a local eye tissue can be constructed.