Provided is a method for producing a liquid food product which is highly stable and can be stored for a long period of time, the liquid food product being highly viscous and containing a naphthoic acid derivative represented by 1,4-dihydroxy-2-naphthoic acid. The method for producing the liquid food product comprises a deoxidation step for deoxidizing a highly viscous liquid raw food product material containing an antioxidant (for example, ascorbic acid and/or erythorbic acid) and a naphthoic acid derivative (for example, 1,4-dihydroxy-2-naphthoic acid), such that the dissolved oxygen level reaches 8 ppm or lower. This method of production can also further comprise a heat-sterilization step. The viscosity of the liquid food product, measured using a B-type viscometer at a temperature of 20°C, is, for example, 20 to 500 mPa·s.
