An aerobic thiamine decomposing bacillus which produces thiaminase I was isolated by the author from human feces. One strain was first found from an adult of Pakistani. Later 12 simlar strains were isolated from patients and healthy subjects living near Taipei city, Taiwan. According to the results of bacteriological, fermentative and immunological investigations about these bacilli, it is obvious that all the strains is belonged to a new species of Genus Bacillus different from hitherto known thiamine decomposing bacilli, Thereafter the same strain was isolated also from feces of a patient in Niigata city. In this paper the experimental results about the morphological and cultural characteristics of this bacillus are mentioned.