Abstract: This invention relates to a balloon and its process which is used in endoscope for observing, diagnosing and curing diseased parts within blood vessel or tubes, a transparent thin film body is provided in forming an inflating portion incorporatedly with an end of a fixing portion wherein the fixing portion is fixed with the end of endoscope, and the transparent thin film body will protect those attachments of endoscope such as light-guide, object glass, optical fiber and the like which are installed in said the end portion of endoscope, wherein it is useful for observation, diagnosis, cure and the like by means of the inflating portion being inflated by injection of physiological salt solution into the interior of inflating portion, in addition a medical laser beam is irradiated so as to be able to cure, that is, the laser beam is transmissible through the balloon itself which is also seeable through.