The invention relates to a process for producing a phosphate, which includes reacting a phosphorus pentaoxide-containing phosphorylating agent with an organic hydroxy compound, the reaction being carried out at a reaction temperature of 50 to 70° C. until the degree (w) of remaining phosphorus pentaoxide undissolved in a reaction solution, defined by the following equation (1), is reduced to 15 wt % or less: W=[1−(AVt−AVp)/AV0]×100  (1) wherein W is the degree [wt %] of remaining phosphorus pentaoxide undissolved in a reaction solution; AVt is the acid value [mg KOH/g] of the reaction solution excluding undissolved phosphorus pentaoxide in an arbitrary time; AVp is the theoretical acid value [mg KOH/g] of the phosphorylating agent excluding undissolved phosphorus pentaoxide; and AV0 is the theoretical acid value [mg KOH/g] of phosphorus pentaoxide.