An insertion system includes an insertion device, a shape sensor, an insertion device holder and an adjustment unit. The insertion device includes an elongated flexible insertion portion. The shape sensor detects a shape of the insertion portion. The insertion device holder holds the insertion device at one end of the insertion portion so that the other end of the insertion portion hangs. The adjustment unit determines an adjustment value to adjust shape detection characteristics of the shape sensor when the insertion device is held by the insertion device holder.
