To efficiently produce a cellulose acetate combined filament yarn having excellent bulkiness and texture by blending a diacetate fiber and a triacetate fiber in spinning.

A method for producing a cellulose acetate combined filament yarn by spinning a diacetate fiber and a triacetate fiber at the same time and blending the fibers, satisfies the following formulas (1) to (3); (1) 0.15Vf/Vja0.50 and 1,200Vja1,650; (2) 0.15Vf/Vjb1.20 and 200Vjb1,650; and (3) 300Vf700, wherein Vf is a take-off speed (m/min) in spinning, Vja is an ejection linear speed (m/min) of a spinning dope of the diacetate fiber through a spinning nozzle, and Vjb is an ejection linear speed (m/min) of a spinning dope of the triacetate fiber through a spinning nozzle.