By means of electron microscope and ultra-thin section technic, the author studied the spore fomation process of B. subtilis and B. anthracis. The results are briefly summarized as follows; 1) The nuclear sites present dispersedly in the cell gradually condense into globe-like young pre-spore in the middle or at the one end of bacterial cell; it increases its' electron dencity with the lapse of time and the the outer coat and the exosporium is formed; the pre-spore condenses and increases its electron dencity forming complete intracellular spore with the sporangium wall, the exosporium, the outer and inner coats outside of it, and with the cortex, the core and the nuclear site inside of it. The sporangium well teart, freeing the spore with exosporium, outer and inner coats. In some ones, both of the sporangium wall and the exosporium tear and the spore with the outer and inner coats is freed. The spore with three coats, the exosporium, the outer and inner coats, sometimes tears its exosporium and frees the spore with the rest two coats. However, the spores with three spore coats are much more than the ones with two coats. 2) In B. anthracis, the dispersed nuclear sites condense into oval or round structure which can be considered the young spore. In some ones, spore coat-like structure can be observed. However, the young intracellular spore never increased its electron dencity, and no cell-free spore could be observed.