To provide a method of producing a uniaxially stretched polytetrafluoroethylene gasket tape, which comprises: (1) a step for preparing a paste comprising a mixture of a polytetrafluoroethylene powder obtained by emulsion polymerization and an extrusion aid, (2) a step for extruding the paste by means of an extruder equipped with a die which has plural separators inside an orifice thereof having a rectangular cross section, (3) a step for rolling, in the extruding direction, an extrudate having slit lines to give a rolled polytetrafluoroethylene sheet, (4) a step for uniaxially stretching the rolled sheet in the rolling direction after removing the extrusion aid from the rolled sheet, and (5) a step for heat-treating the obtained uniaxially stretched polytetrafluoroethylene sheet. The die of the extruder has plural sheet-like separators in the orifice thereof having a rectangular cross section. The separators are mounted so that free ends thereof are located at a point exceeding a center point of a long side of the orifice, and function to provide slit lines inside the extrudate in parallel with the long side of the orifice. The high performance inexpensive PTFE gasket tape is produced by the uniaxially stretching method and has properties equal to those of biaxially stretched PTFE gasket tape.