Process evaluation on a large-scale plant by the high pressure synthesis method (Haber method) and the low pressure / low temperature synthesis method under development was studied and a new process of the small-scale plant (synthesis process / low pressure method, separation process / absorption method) was proposed. The new process is extremely simple without high pressure equipment and construction costs are less than half. It is necessary to develop and verify the catalyst performance in low pressure / low temperature method and ammonia absorbent performance for NH₃ separation.