β-Glucan is a natural compound contained in cell walls of yeast or fungi, and cereal’s fiber. It is also known to boost the immune system in human. Aureobasidium is a producer of water-soluble β-1,3/1,6-glucan. In this study, natural killer (NK) cell and macrophage activity were tested to investigate the effects of β-1,3/1,6-glucan isolated from A. pullulans on immune activity. Activation of NK cell was increased about 63-39% by the treatment of 10-200 μg/mL β-1,3/1,6-glucan than control. Besides, only 10 μg/mL of β-1,3/1,6-glucan was enough to boost activation of NK cell. Phagocytosis of macrophage was increased to 15~21% by the treatment of 10~200 μg/mL of β-1,3/1,6-glucan than zymosan-treatment. In LP-BM5 proliferating inhibition test, relative mRNA level of LP-BM5 virus was decreased in β-1,3/1,6-glucan-treated cell about 36~74% than control. The decline of LP-BM5 mRNA level appeared to depend on the concentration of β-1,3/1,6-glucan. These results suggest that pure β-1,3/1,6-glucan from A. pullulans might be contributing to enhancement of immune activity through the activation of NK cell and phagocytosis of macrophage. Moreover, treatment of the β-1,3/1,6-glucan could increase the resistance to virus infection such as LP-BM5 through the restraining of the multiplication.