Provided are a process for producing a phosphate and a process for stabilizing a phosphate, the phosphate being an acid-form phosphate wherein an organic hydroxy compound is an alkylene oxide adduct. A production process of a phosphate and a stabilization process of a phosphate, including the step 1 of reacting an organic hydroxy compound represented by the following general formula (I) with a phosphorylating agent: R.sup.1--O--(AO).sub.n--H (I) wherein R.sup.1 represents a straight or branched alkyl group or alkenyl group having 6 to 36 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n is a number of 0.1 to 100 on the average; the step 2 of purifying the reaction product obtained in the step 1 until the content of the organic hydroxy compound that has not yet reacted becomes 2% or less by weight; and the step 3 of adding water to the purified product obtained in the step 2 at such a ratio that the content of water in the final product is from 0.5 to 10% by weight.