The coating agent of the present invention is represented by the polyorganosiloxane (1) represented by the following general formula (1), the polydiorganosiloxane (2) represented by the following general formula (2), and the following general formula (3). Any one of an amino group-containing polyorganosiloxane (3) and a hydroxyl group-containing polyorganosiloxane (4) represented by the following general formula (4). ADVANTAGE OF THE INVENTION According to this invention, the medical device (especially needle hook) formed by surface-treating (application coating) with the coating agent which the piercing characteristic improved, and the said coating agent is provided.本発明のコーティング剤は、下記一般式（１）で示されるポリオルガノシロキサン（１）と、下記一般式（２）で示されるポリジオルガノシロキサン（２）と、下記一般式（３）で示されるアミノ基含有ポリオルガノシロキサン（３）および下記一般式（４）で示される水酸基含有ポリオルガノシロキサン（４）のいずれか一方と、を含む。本発明によれば、刺通特性が向上したコーティング剤および当該コーティング剤で表面処理（塗布）されてなる医療機器（特に、針）が提供される。
