A thermoformable medical member and heater and a method for manufacturing the same are disclosed. The thermoplastic material is converted from a relatively rigid state to a moldable state in a relatively narrow temperature range and returned to a clinically rigid state in a relatively short time. This state is maintained even when the outside air temperature is high. [Selection] Figure 1【解決手段】 熱成形可能な医療用部材及びヒータならびにその製造方法が開示される。熱可塑性の材料を、比較的硬質な状態から成形可能な状態へと比較的狭い温度範囲で転換し、比較的短時間の間に臨床的に硬質な状態に戻す。外気温度が高くともその状態を維持させる。【選択図】 図1