This study is the fundamental report to propose the capability of discarded Bentonite by heat-treatment as concrete mineral admixture. The experiment is performed by flow test of mortar and by compressive strength of 7, 14, 28, 91 days, As a result of experiment about mortar using discarded Bentonite by heat-treatment, in the case of $500^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$, $800^{\circ}C$.60min, compressive strength is superior to the every situation than plain Mortar. Especially, in the case of $700^{\circ}C$.60min, as strength activity index is measured by 109%, it can be applied as concrete mineral admixture. But, flow of Mortar using discarded Bentonite by heat-treatment is decreased about 2.5cm in the case of 30min and about 1.7cm in the case of 60min.