A medical device body, such as capsule body that is inserted in a body cavity, is provided with a thrust force-generating mechanism generating thrust force by a helical projection, etc. An information-providing portion is formed by at least either a memory portion where the condition of the thrust force-generating mechanism is memorized or a direction-detecting portion for detecting the directionof the medical device body. When the direction of thrust force generation by the thrust force-generating mechanism is directed by an input portion, a control portion varies continuously or in other manners the condition of thrust force generation by the thrust force-generating mechanism based on information from the information-providing portion.
