A treatment device includes: a balloon a biologically active agent part applied on an outer surface of the balloon a protective sleeve encircling the balloon and being displaceable proximally and an interposed member having a self-expanding function arranged between the balloon and the protective sleeve. When the protective sleeve is moved proximally in order for the balloon to be exposed to the inside of a blood vessel, the presence of the interposed member prevents the biologically active agent part from being scraped and peeled off by THE inner surface of the protective sleeve.
