Maximum hardness of a flexible tube section of an endoscope is set such that substantial maximum hardness at a time when an over-tube is attached is equal to or lower than maximum hardness of a flexible tube section of an endoscope. That is, the maximum hardness of the flexible tube section of the endoscope is set substantially equal to hardness obtained by subtracting hardness of the over-tube itself from the maximum hardness of the flexible tube section of the endoscope. In the endoscopes including a hardness changing function, maximum hardness of the endoscope, to which the over-tube is not attached, and maximum hardness of the endoscope, to which the over-tube is attached, are set substantially equal.
