PURPOSE: To obtain a combined filament polyester yarn having spun silk tone with dyeing unevenness having high surface variety by nearly completely keeping the bulkiness in latent state in the weaving or knitting stage and developing the bulkiness by treating with boiling water after finishing to a woven fabric or knit fabric.

CONSTITUTION: A filament A is unwound from a package 1, drawn between nip rollers 2-5 and supplied to a compressed air turbulent flow processing apparatus 6. The stock yarn is drawn by neck-drawing at a draw ratio corresponding to 50-95% of the natural draw ratio (NDR). The boiling water shrinkage of the drawn filament A is made to be lower than that of the filament B by raising the drawing temperature or the temperature of a hot plate 4 above the second- order transition point. The filament B to be used as a core yarn is unwound from a package 11, supplied to the compressed air turbulent flow processing apparatus 6 via a roller 12, doubled with the filament A to form a loop yarn, subjected to stretch treatment between rollers 7 and 8 and wound to obtain the objective combined filament yarn.