A search for the neutrinoless double-beta decay of 124Sn was carried out using the tin-loaded liquid scintillator for an active source-detector technique. Tin (32.6%) in weight was successfully loaded into the liquid scintillator, and light output was as high as 57% of the unloaded liquid scintillator. A tin-loaded liquid scintillator with 1.1ℓ volume was installed at the 700m underground laboratory in YangYang, and data were taken for 5285h. No evidence for the 0νββ decay was found and a lower limit on the 124Sn half-life was obtained to be 2.0×1019year with 90% C.L. The new limit represents a significant improvement with respect to those previously available for 124Sn.