A reflection teaching aid includes a mounting board and first and second plane mirrors. The mounting board has a plurality of slots that are angularly displaced from each other. When inserting edges of the first and second plane mirrors are inserted respectively into two selected ones of the slots, and when an object is disposed between reflective surfaces of the first and second plane mirrors, a selected one of included angles is formed between the reflective surfaces of the first and second plane mirrors, thereby permitting an object placed between the reflective surfaces of the first and second plane mirrors to generate a corresponding number of reflected images of the object.