22 implanted with carbon to the end after the cleaned stent 22 is fixed to the tubular reactor 11 made of pyrex glass tube the internal pressure of the reactor 11 is lowered by atmospheric pressure of up to 0 01 by use of the vacuum pump 20 and oxygen argon or a mixture gas of argon and hydrogen is introduced into the reactor 11 to maintain the pressure at 0 05 to 5 0 torr the plasma is generated in the radiator by applying a discharge power of 5 to 200 w to the electrodes from the rf power supply source 13 during 1 to 30 minutes it is preferable that the discharge power is 50 w or more and the processing time is 10 minutes or more in order to sufficiently clean and activate the surface of the stent 22 after the surface activating process is completed the internal pressure of the reactor is lowered by atmospheric pressure of up to 0 01 and diaminocyclo hexane dach monomer is introduced into the reactor 11 to maintain the reactor 11 at atmospheric pressure of 0 05 to 1 0 the plasma is generated in the reactor by applying a discharge power of 50 to 100 w to the electrodes from the rf power supply source 13 during 1 to 30 minutes preferably 15 to 20 minutes introduction of an amine radical is preferable above 15 minutes but a thin film to be coated may be too thick if it is performed during above 20 minutes in this instance the internal stress in highly increased and thus the coated thin film may be peeled off from the surface of the stent 22 it is preferable.