PURPOSE: To obtain the compound useful for a synthetic intermediate of sulfonylurea, a herbicide, in one step and in a high yield, by reacting a propanediimidate with a salt of cyanamide in an alcohol.

CONSTITUTION: A propanediimidate or its salt of formula I (X, Y are each O, S; R1, R2 are each C1-4 alkyl, C1-4 alkoxy, C1-2 alkyl, haloC1-4 alkyl) is reacted with a salt of cyanamide of formula II (R3 is alkali metal, alkaline earth metal cation; j is 1, 2; k is 0, 1). The subject compd. of formula III is obtained by dissolving a compd. of formula I and II in an alcohol of the formula R4 -OH (R4 is C1-6 alkyl), pref. at a temperature of -10-10°C, and pouring the obtained solution into an inactive organic solvent of a temperature of 100°C or higher, eliminating the alcohol by distillation.