PURPOSE: To sharply reduce the production of thread cut by polymerizing a plurality of a heatproof cloth such as glass fiber and flame-proof fiber, making a twisting twine mainly composed of a glass fiber thread and a para-alamide fiber thread as a thread to integrally sew.

CONSTITUTION: A polymer heatproof cloth 1 is polymerized through reinforcing middle cores 2,2 between two thick heatproof cloths 3, 3 and these are integrally sewed with threads 4, 4, 5, 5, 6, 6 consisting of twisting twine mainly composed of a glass fiber thread and a para-alamide fiber thread by the use of a multi- sewing machine. Two heatproof members 7, 7 are obtained by cutting the polymer heatproof cloth 1 along a center line A-A'. Thereby the tread and a knitting woof can be prevented from being cut while production efficiency can be heightened.