Maximum hardness Hmax2 of a flexible tube section 13A of an endoscope 2A is set such that substantial maximum hardness Hmax2' at a time when an over-tube 70 is attached is equal to or lower than maximum hardness Hmax1 of a flexible tube section 13 of an endoscope 2. That is, the maximum hardness Hmax2 of the flexible tube section 13A of the endoscope 2A is set substantially equal to hardness obtained by subtracting hardness of the over-tube 70 itself from the maximum hardness Hmax1 of the flexible tube section 13 of the endoscope 2. In the endoscopes 2 and 2A including a hardness changing function, maximum hardness of the endoscope 2, to which the over-tube 70 is not attached, and maximum hardness of the endoscope 2A, to which the over-tube 70 is attached, are set substantially equal.
