[ ${eta}$ ]-1,3-Glucans enhance immune reactions such as antitumor, antibacterial, antiviral, anticoagulatory, and wound healing activities. ${eta}$-1,3-Glucans have various functions depending on the molecular weight, degree of branching, conformation, water solubility, and intermolecular association. The molecular weight of the soluble glucan was about 15,000 as determined by a high-performance size exclusion chromatography. From the infrared (IR) and $^{13}C$ NMR analytical data, the purified soluble glucan was found to exclusively consist of ${eta}$-D-glucopyranose with 1,3 linkage. We tested the immunestimulating activities of the soluble ${eta}$-1,3-glucan extracted from Agrobacterium sp. R259 KCTC 1019 and confirmed the following activities. IFN-$_{gamma}$ and each cytokines were induced in the spleens and thymus of mice treated with soluble ${eta}$-1,3-glucan. Adjuvant effect was observed on antibody production. Nitric oxide was synthesized in monocytic cell lines treated with ${eta}$-1,3-glucan. The cytotoxic and antitumor effects were observed on various cancer cell lines and ICR mice. These results strongly suggested that this soluble ${eta}$-1,3-glucan could be a good candidate for an immune-modulating agent.