To conduct a randomized controlled trial comparing chemotherapy using UFT/LV and immunochemotherapy using UFT/LV combined with PSK in patients with histological stage IIIa and IIIb colorectal cancer (adenocarcinoma) who have undergone curative surgery without residual cancer (R0) using 3-year disease-free survival rate as primary endpoint, and also to analyze the 3-year overall survival, compliance, adverse events, QOL and relationship with tumor factors.