An unsintered polytetrafluoroethylene tape for sealing screw joints is described. The tape is obtained by uniaxially stretching an unsintered body of a composition comprising 75 to 25 wt. parts of polytetrafluoroethylene fine powder and 25 to 75 wt. parts of inorganic powder which has new Mohs hardness of 3 or less and substantially no water absorption. The tape has excellent heat stability and sealing properties like a conventional polytetrafluoroethylene tape for screw joint sealing, but the required amount of PTFE can be decreased. Furthermore, by compounding a specific inorganic filler, the tape does not suffer from limitations regarding stretching conditions, and does not abrade or damage the screw.