The present invention provides a medical device for placement into a lumen such as a stent and a catheter whose surface is uniformly and sufficiently coated with a drug, and a process thereof with easy way and with low cost. The medical device is coated with mixed particles of drug particles whose surface is modified with positive-charge and biocompatible nanoparticles. In the invention, a drug can be taken into a cell through the dissolution of the drug particle together with the biocompatible nanoparticle after a DES is placed in a biological body.