The invention provides a composition of a mixture containing a first phenylaminopyrimidinyl indole derivative and phenylaminopyrimidinyl indole derivative which are different from each other. The mixture can have synergistic antibacterial effects on streptococcus parasanguis, staphylococcus cohnii, neisseria gonorrhoeae, peptostreptococcus prevotii, staphylococcus hominis, serratia liquefaciens, achromobacter xylosoxidans, mycobacterium murinum, corynebacterium macginleyi, morganella morganii, staphylococcus capitis, streptococcus sanguis, streptococcus pyogenes, peptostreptococcus anaerobius,alkali cellulase producing chryseomonas luteola, aeromonas caviae, enterobacter cloacae, micrococcus luteus, dendritic microbacterium and legionella pneumophila with extracts of plants such as broad-leaved echinops roots, stonecrop, cyrtomium rhizomes, standish's lonicera and rhizoma alocasiae macrorrhizae.