1. A categorizing apparatus comprising: a processor programmed in accordance with instructions stored in memory to determine a first position of a selected object selected by a user, in a first region, from among objects arranged in the first region on a display screen; said processor being further programmed in accordance with instructions stored in memory to identify, among the objects, one or more related objects which are related to the selected object; said processor being further programmed in accordance with instructions stored in memory to assign a parameter to each of the related objects, including the selected object, according to a degree of relatedness between each of the one or more related objects and the selected object, the parameter contributing to a predetermined relationship which defines a tracking property of each of the related objects to the selected object when the selected object is moved from the first position; and said processor being further programmed in accordance with instructions stored in memory to cause, when the user moves the selected object from the first position to a second position, the related objects to follow the selected object and move the related objects to predetermined positions according to the degree of relatedness, the predetermined positions being set with the second position as an origin, and the second position being included in a second region that differs from the first region on the display screen, wherein the selected object and the related objects are placed in dispersal in the first region without using the degree of relatedness, and said processor is further programmed in accordance with instructions stored in memory to spatially reorganize and arrange the related objects at the predetermined positions when the user causes the related objects to follow the selected object to move to the predetermined positions, said processor is further programmed in accordance with instructions stored in memory to detect a velocity of the selected object when the user moves the selected object from the first position to the second position; and said processor is further programmed in accordance with instructions stored in memory, in a case where a magnitude of the velocity detected is greater than or equal to a first threshold, to return, to an original place in the first region, a related object which is included in the related objects and whose degree of relatedness is equal to or smaller than the first threshold.