An improved yarn constituted of expanded graphite and PTFE is provided in which the expanded graphite as a core material is not exposed and which can be easily produced. The yarn is formed by: forming a base (3) by wrapping an expanded-graphite sheet material (1) with a PTFE film (2) while keeping the PTFE film (2) and the expanded-graphite sheet material (1) equally oriented with respect to longitudinal direction; and twisting the base (3). The base (3) has an approximately circular section, and is composed of the expanded-graphite sheet material (1) having a rounded sectional shape and the pipe-form rounded PTFE film (2) with which the sheet material (1) has been wrapped.
