To obtain the subject compound and its salt by production improved method by using an aminomalonic ester or a malonic ester and adding catalytic hydrogen in an inert solvent in which the addition of hydrogen is performed in the presence of a drying agent and solvent, etc.

An aminomalonic ester of the formula I (R' and R" are each an alkyl or an aryl, etc.) and an aminomalonic ester salt of the formula II {Y is an acid anion; (n) is a basicity of an acid HnY}, as the case may be, is produced by adding a substituted malonic ester of the formula III (X is nitro or nitroso, etc.) into an inert solvent (e.g. n-heptane) and an acid HnY (e.g. HCl, sulfuric acid, etc.), as the case may be, to a hydrogen-added mixture, then adding catalytic hydrogen in the presence of a drying agent and a solvent, etc. In the reaction, 0.0001-0.05 pt.wt. of a noble metal catalyst is used to 1 pt.wt. of the compound of the formula [[ and ≥0.02 pt.wt., preferably 0.02-4 pts.wt. of the solid drying agent is used. The reaction is performed at 0-100°C, preferably 0-50°C under 1-150 bar (absolute pressure) hydrogen pressure. Water is removed by heating the used drying agent at 100-300°C in an inert gas.