This study was intended as an application for the preparation of flowing concrete using natural humic acid. Slump test, slumpflow test, L type test and V-lot test were carried out to check the workability characteristics of fresh concrete with two kinds of W/C ratio, 40% and 50%. The mechanical properties of hardened concrete were also investigated in terms of compressive strength and splitting tensile strength. At the results of this experimental study, the fluidity of fresh concrete was increased at the addition ratio of humic acid ranged from 0.6% to 1.8%, and decreased where the ratio exceed 2.4%. Flow test and L type test also showed the similar variation. The compressive strength variation was ranged 60~70 kgf/cm(2), and the splitting tensile one was ranged 10~12 kgf/cm(2), and the maximum strength was appeared at 1.2% addition ratio of humic acid.