A process for synthesizing a halogenated nitrogen represented by a formula of NF x L 3-x , where L represents a halogen other than fluorine, and 1 x 3 is provided. This process includes the step of (a) reacting an ammonium complex compound that is one selected from the group consisting of NH 4 F&peseta;nHF, (NH 4 ) y MF z &peseta;mHF and a mixture of these and that is in liquid form, with an interhalogen compound or a mixture of an interhalogen compound and F 2 gas, wherein 1<n, 1 y 4, 2 z 8, 0.1 m, and M represents one selected from the group consisting of elements of group 1 to group 16 of periodic table and a mixed element of these elements.