A yarn which is configured by using expanded graphite and PTEE is provided while improving the yarn so that the expanded graphite functioning as a core member is not exposed and it can be simply produced. Therefore, a yarn is formed by: forming a base member 3 configured by enveloping an expanded graphite sheet member 1 with a PTEE film 2, in a state where the PTEE film 2 and the expanded graphite sheet member 1 are aligned with each other in longitudinal direction; and twisting the base member 3. The base member 3 has an approximately circular sectional shape, and is configured by enveloping the expanded graphite sheet member 1 having a rounded sectional shape with the PTEE film 2 which is rounded in a pipe-like shape.