Disclosed is an optical fiber coating apparatus for preventing generation of bubble in a coating layer of an optical fiber when the optical fiber is coated, which includes a coating unit for allowing an optical fiber to pass through and forming a coating layer on the optical fiber; a base coupled with a lower portion of the coating unit to draw the optical fiber; a cover installed to an upper portion of the coating unit to isolate the coating unit from an external air and having an optical fiber introduction hole; a gas supply line for supplying gas, having smaller kinetic viscosity than the air, into an inner space formed by the cover; and a coating agent discharge line for discharging a coating agent remained in the inner space of the cover. The inner space forms positive pressure circumstance by using the gas having smaller kinetic viscosity than the air.