The present invention relates to an agent for activating mammalian sperm and a method for activating sperm by use of the activating agent. More specifically, the present invention relates to a sperm activating agent containing endo--galactosidase and/or FGF, which accelerate motility of mammalian sperm, for use in in-vitro fertilization and artificial insemination by husband and a sperm activating method by adding endo--galactosidase and/or FGF.