A guide body can be prevented from being disengaged from a track rail even where the track rail is made of a low-rigidity material, thereby securing reliable movement along the track rail. The guide body includes: a large number of rolling elements that roll on a rolling surface formed along a structure, the guide body being movable relative to the structure; an endless circulation path through which the large number of rolling elements circulate; a load opening portion for allowing the large number of rolling elements in the endless circulation path to be held in contact with the rolling surface of the structure; and a guide portion formed on at least one side of the load opening portion so as to project toward the structure side with respect to projecting ends of the large number of rolling elements projecting from the load opening portion toward the structure side.