A method for collecting a compound of general formula (III) from a liquid phase component that is formed as a by-product in a method for producing a compound of general formula (I), comprising: step (A): a step for mixing the liquid phase component, water, and the compound of general formula (III); step (B): a step for reacting the liquid phase component with water in a reactor; and step : a step for discharging, as a liquid phase component inside the reactor, a reaction liquid formed in step (B) and containing the compound of general formula (III) to an outside of the reactor, in the general formula (I), R 11 represents a monovalent to trivalent organic group, and n11 represents an integer of 1 to 3, and in the general formula (III), R 31 represents a monovalent to trivalent organic group, and n31 represents an integer of 1 to 3, wherein the compound of general formula (III) is diaminohexane, diaminotoluene, diaminomethyltrimethylcyclohexane, dicyclohexylmethane diamine, diphenylmethane diamine, isophorone diamine, hexamethylene diamine, pentamethylene diamine, xylylene diamine, bis(aminopropyl)benzene, bis(aminopropyl)cyclohexane, or aminomethyloctane diamine, wherein the liquid phase component that is formed as a by-product in the method for producing the compound of general formula (I) is a liquid phase component extracted from a thermal decomposition reactor when a gas phase component comprising the compound of general formula (I) generated by supplying a liquid containing a carbamate produced from a carbonic acid derivative, a hydroxy compound and the compound of general formula (III) to the thermal decomposition reactor and then subjecting the carbamate to thermal decomposition reaction is collected, and wherein the carbonic acid derivative is urea or a carbonic acid ester. step (A): a step for mixing the liquid phase component, water, and the compound of general formula (III); step (B): a step for reacting the liquid phase component with water in a reactor; and step : a step for discharging, as a liquid phase component inside the reactor, a reaction liquid formed in step (B) and containing the compound of general formula (III) to an outside of the reactor, in the general formula (I), R 11 represents a monovalent to trivalent organic group, and n11 represents an integer of 1 to 3, and in the general formula (III), R 31 represents a monovalent to trivalent organic group, and n31 represents an integer of 1 to 3, wherein the compound of general formula (III) is diaminohexane, diaminotoluene, diaminomethyltrimethylcyclohexane, dicyclohexylmethane diamine, diphenylmethane diamine, isophorone diamine, hexamethylene diamine, pentamethylene diamine, xylylene diamine, bis(aminopropyl)benzene, bis(aminopropyl)cyclohexane, or aminomethyloctane diamine, wherein the liquid phase component that is formed as a by-product in the method for producing the compound of general formula (I) is a liquid phase component extracted from a thermal decomposition reactor when a gas phase component comprising the compound of general formula (I) generated by supplying a liquid containing a carbamate produced from a carbonic acid derivative, a hydroxy compound and the compound of general formula (III) to the thermal decomposition reactor and then subjecting the carbamate to thermal decomposition reaction is collected, and wherein the carbonic acid derivative is urea or a carbonic acid ester. <EOS>