Microneedles soluble in the skin and having improved residence time in the body, the microneedles comprising surface-modified microspheres encapsulating a drug, wherein the surface-modified microspheres are biodegradable and have a surface on which a dimple structure is formed, wherein the microspheres are prepared by solvent evaporation method comprising: i) preparing an oil phase by dissolving a drug and a surfactant-acting biodegradable polymer in an organic solvent; ii) forming an O/W, oil-in-water, emulsion by mixing the oil phase with a water phase in which a water-soluble polymer is dissolved; and iii) obtaining surface-modified microspheres by evaporating the solvent from the O/W emulsion, the evaporation performed under stirring at a speed of 800 to 1,000 rpm; and wherein: - the surfactant-acting biodegradable polymer is poly(lactate-co-glycolate) (PLGA); - the water-soluble polymer is polyvinyl acetate; - the drug is tacrolimus; and - a soluble material for forming the microneedles is any one selected from the group consisting of alginic acid, hyaluronic acid, dextran, cellulose, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, sodium carboxymethylcellulose, polyalcohol, cyclodextrin, dextrin, trehalose, sucrose, lactose, mannitol, xylitol and mixtures thereof. wherein the surface-modified microspheres are biodegradable and have a surface on which a dimple structure is formed, wherein the microspheres are prepared by solvent evaporation method comprising: i) preparing an oil phase by dissolving a drug and a surfactant-acting biodegradable polymer in an organic solvent; ii) forming an O/W, oil-in-water, emulsion by mixing the oil phase with a water phase in which a water-soluble polymer is dissolved; and iii) obtaining surface-modified microspheres by evaporating the solvent from the O/W emulsion, the evaporation performed under stirring at a speed of 800 to 1,000 rpm; and i) preparing an oil phase by dissolving a drug and a surfactant-acting biodegradable polymer in an organic solvent; ii) forming an O/W, oil-in-water, emulsion by mixing the oil phase with a water phase in which a water-soluble polymer is dissolved; and iii) obtaining surface-modified microspheres by evaporating the solvent from the O/W emulsion, the evaporation performed under stirring at a speed of 800 to 1,000 rpm; and wherein: - the surfactant-acting biodegradable polymer is poly(lactate-co-glycolate) (PLGA); - the water-soluble polymer is polyvinyl acetate; - the drug is tacrolimus; and - a soluble material for forming the microneedles is any one selected from the group consisting of alginic acid, hyaluronic acid, dextran, cellulose, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, sodium carboxymethylcellulose, polyalcohol, cyclodextrin, dextrin, trehalose, sucrose, lactose, mannitol, xylitol and mixtures thereof. - the surfactant-acting biodegradable polymer is poly(lactate-co-glycolate) (PLGA); - the water-soluble polymer is polyvinyl acetate; - the drug is tacrolimus; and - a soluble material for forming the microneedles is any one selected from the group consisting of alginic acid, hyaluronic acid, dextran, cellulose, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, sodium carboxymethylcellulose, polyalcohol, cyclodextrin, dextrin, trehalose, sucrose, lactose, mannitol, xylitol and mixtures thereof.