PURPOSE: To obtain a covered yarn having high interlace pin count by drawing a core yarn, interlacing a covering yarn to the core yarn with a jet fluid and subjecting the resultant covered yarn to an additional interlacing treatment using another jet fluid.

CONSTITUTION: A yarn 21 is drawn between the first and second feed devices 1 and 2 to use the drawn yarn as a core yarn and a covering yarn 31 is interlaced to the core yarn with the first interlacing nozzle 6. The resultant covered yarn 41 is subjected to an additional interlacing treatment with the second interlacing nozzle 8 and wound by a winding device 9.