[Problem]A microbial pesticidal composition containing viable spores of a bacterium belonging to the genus Bacillus and a chemical pesticide, in which the spores can be preserved stably in a living state for a long period of time, and a method for preserving the spores stably in a living state for a long period of time, are provided.[Dissolution Means]Viable spores of Bacillus subtilis and/or Bacillus amyloliquefaciens are blended with at least one member selected from a metal oxide, a metal hydroxide, a metal oxide silicic acid salt, and a metal hydroxide silicic acid salt.