In order to find new genetic sources of rice salt tolerance, we did screening with about 10,000 rice mutant lines created by Ac/Ds insertional mutagenesis. First, we raised rice seedlings with media soil on 0.7% NaCl solution and selected 71 putative salt tolerant lines and analyzed their Ds insertion sites. We tested their salt tolerance by growing seedlings on MS medium containing, 0 mM, 150 mM, and 250 mM NaCl. Also, their seedling salt tolerance were evaluated by growing on Yoshida nutritional solution containing 0.6% NaCl. Finally, we selected eight mutant lines showing increased seedling salt tolerance compared with wild type variety, Dongjin, repeatedly. We grow them in rice field and investigated their agronomic traits such as heading time, culm length, panicle length, and panicles per hill. Among them two lines which were named Salt10 and Salt23 and showed favorable agronomic characteristics were crossed with Dongjin for further genetic analysis and mapping the causative gene variation.