A rotation mechanism includes a mandrel, a rotation axle, a needle roller bearing and an angular bearing. The mandrel includes a shaft portion, a first annular contact portion and a second annular contact portion. The shaft portion has an outer surface, and the first annular contact portion and the second annular contact portion are located on the outer surface and respectively surround the axis of the mandrel. The rotation axle includes an annular portion, a third annular contact portion and a fourth annular contact portion. The annular portion has a shaft hole and an inner surface forming the shaft hole. The third annular contact portion and the fourth annular contact portion are located on the inner surface, and the mandrel passes through the shaft hole. The needle roller bearing is in contact with the first annular contact portion and the third annular contact portion, and is located between them.