A novel immunostimulatory oligonucleotide by which an IFN-inducing activity is enhanced and an inflammatory cytokine-inducing activity is reduced, and a pharmaceutical containing the same, and an aplication thereof are provided. That is, the present invention provides the immunostimulatory oligonucleotide composed of a base sequence represented by a formula: 5'-(G) M PXCGYQ(G) N -3' (X and Y are mutually independent and represent an arbitrary sequence which has a length of 0 to 10 nucleotides and does not contain 4 or more consecutive G residues, and a length of X + Y is 6 to 20 nucleotides； XCGY contains a palindrome sequence having a length of at least 8 nucleotides and has a length of 8 to 22 nucleotides； P and Q are mutually independent and represent one nucleotide other than G； M represents an integer of 6 to 10 and N represents an integer of 0 to 3) wherein a full length thereof is 16 to 37 nucleotides (except for an oligonucleotide composed of a basesequence represented by SEQ ID NO:5), the pharmaceutical application thereof.
