Fuente: WIPO "milk" The serotonin production-promoting composition contains one kind or more selected from a bacterium which is Bifidobacterium bifidum MCC2085 (NITE BP-03881), a culture of the bacterium and a processed product of the bacterium. The serotonin production-promoting composition contains one kind or more selected from a bacterium which is Bifidobacterium longum subsp. infantis M-63 (NITE BP-02623), a culture of the bacterium and a processed product of the bacterium.