Rice is one of the most important crops of North Bihar, but its yield is quite less. A major constraint of paddy production is non-availability of quality seed in Bihar. Certified seed can be produced, to make farmers selfsufficient in seed and achieve high productivity. An experiment was conducted in Supaul district of N. Bihar in the year 2009 and 2010 at farmers' field, under the supervision of Krishi Vigyan Kendra, Supaul. The objective of the study was to calculate and compare the economics of production of paddy seed variety Rajendra Mahsuri -1 (certified) in farmers' field to commercial paddy grain. The identified village was Jahlipatti under Raghopur block which is located 6 km South to KVK, Supaul. On the basis of the data generated from the experiment of paddy seed production it was found that the benefit cost ratio of commercial grain produced was only 1.7: 1, whereas paddy seed had higher cost benefit ratio of 2.5:1. This implies that the profit which is obtained is more than twice the cost involved in this enterprise. The paddy seed production is a rewarding enterprise for Supaul Farmers giving high monetary returns.