Demand for dementia prevention has been increasing in recent years. Cognitive training is being carried out to improve cognitive function as one of dementia prevention methods. In order to realize the training of cognitive functions for elderly people required in daily life, this study examined the difficulty control method for change detection task using everyday object images. This task presents a subject five everyday objects on a display and asks him/her to detect an object rotated after a timeinterval. From the experimental results, it was found that the correct answer rate is high when the appearances of the object before and after rotation are similar,whereas the correct answer rate is low when the rotated object is spatially isolated from the other objects. It was suggested that the difficulty level could be adjusted by the positional relationship between these objects and the visual similarity before and after rotation.