Rigidity variable apparatus, endoscope, and manufacturing method of rigidity variable apparatus

A manufacturing method of a rigidity variable apparatus comprising:

• filling a filler into an inside of a rigidity variable member in a radial direction, the rigidity variable member being formed in a cylindrical shape having a first opening at one end portion, a bending rigidity of the rigidity variable member increasing by being heated, the filler being filled through the first opening;
• and
• passing a heater unit having a cylindrical shape through the first opening and pushing the heater unit into the inside of the rigidity variable member, the heater unit including a heater having a cylindrical shape and a tube arranged on an inside of the heater in the radial direction, to arrange the filler so as to fill a gap between an inner circumferential surface of the rigidity variable member and the heater.