Provided is an apparatus for producing a carbon nanotube fiber. The apparatus includes: a vertical reactor having a reaction zone; an inlet through which a spinning solution is introduced into the bottom of the reaction zone of the reactor; an inlet through which a carrier gas is introduced into the bottom of the reaction zone of the reactor; heating means for heating the reaction zone; and a discharge unit disposed on the top of the reaction zone and through which a carbon nanotube fiber is discharged from the reactor. The spinning solution entering the reaction zone through the spinning solution inlet is carbonized and graphitized while ascending from the bottom of the reaction zone by the carrier gas entering through the carrier gas inlet, to form a carbon nanotube fiber consisting of continuous aggregates of carbon nanotubes. Further provided is a carbon nanotube fiber produced using the apparatus. The carbon nanotube fiber is long and exhibits high electrical conductivity, tensile strength, and elasticity. Due to these advantages, the carbon nanotube fiber is expected to find a variety of applications, including multifunctional composite materials, deformation/damage sensors, transmission cables, and electrochemical devices, for example, microelectrode materials for biological substance detection, supercapacitors, and actuators.