The present invention aims to provide an immunostimulating agent superior in an immunostimulatory effect, particularly a compound useful as a vaccine adjuvant, a pharmaceutical composition containing the compound, a vaccine containing the compound and an antigen. The present invention relates to an immunostimulating agent containing at least one kind of a compound represented by the formula (I) : wherein each symbol is as defined in the DESCRIPTION, or a salt thereof, or at least one kind of a compound represented by the formula (II) : wherein each symbol is as defined in the DESCRIPTION, or a salt thereof.