The present invention relates to a medicament for treating cancer or infectious disease, the medicament comprising an immune checkpoint blockade and an adjuvant composition. More specifically, the present invention relates to a medicament for cancer or infectious diseases, wherein an anti-PD-1 antibody or an anti-PD-L1 antibody is used in combination with a nucleic acid adjuvant composed of a double-stranded RNA and a single-stranded ODN.