To provide a process which efficiently produces an ester of nitrous acid with the use of a nitrogen oxide without employing a salt of nitrous acid.

A nitrogen oxide (particularly, a nitrogen oxide containing at least N2O3) is reacted with an alcohol at a reaction temperature of lower than 10C (for example, about -30 to 3C). According to such a method, even with the use of a secondary alcohol or a tertiary alcohol, the corresponding ester of nitrous acid is obtained in a high yield (for example, a yield of not less than 80 mol% on a nitrogen oxide basis).