Provided are a drug coat layer capable of suppressing breakage of a long drug crystal on the surface of a balloon and maintaining the drug crystal in an appropriate shape for acting on a living body, and a method for forming the drug coat layer. A plurality of drug coat layers (40) formed on the surface of the balloon (30), which are crystals of a water-insoluble drug having a long axis extending from the surface of the balloon (30) at various lengths and angles. A plurality of the elongated bodies (42) located outside the aggregate (50) of the plurality of elongated bodies (42) so as to fill the space between the elongated body (42) and the elongated body (42). It has a water-soluble additive layer (41) provided in the space between the outer surface (51) having an uneven surface connecting the tip (46) and the side surface (43) and the surface of the balloon (30), and has a length. The tip of the scale body (42) hardly protrudes from the additive layer (41), and the side surface (43) and / or the tip surface (47) of the long body (42) is exposed on the surface of the additive layer (41). are doing.バルーンの表面の長尺な薬剤結晶の破損を抑制し、薬剤結晶を、生体に作用させるために適切な形状で維持できる薬剤コート層およびその形成方法を提供する。 バルーン（３０）の表面に形成される薬剤コート層（４０）であって、バルーン（３０）の表面から種々の長さおよび角度で延在する長軸を有する水不溶性薬剤の結晶である複数の長尺体（４２）と、長尺体（４２）の間を満たすように、複数の長尺体（４２）の集合体（５０）の外側に位置する当該長尺体（４２）の複数の先端（４６）および側面（４３）を繋ぐ凹凸を備えた外面（５１）とバルーン（３０）の表面との間の空間に設けられる水溶性の添加剤層（４１）と、を有し、長尺体（４２）の先端が添加剤層（４１）からほぼ突出せず、長尺体（４２）の側面（４３）および／または先端面（４７）が添加剤層（４１）の表面に露出している。
