Disclosed is radiation tomography apparatus for smaller animals including a radiation source for emitting radiation; a radiation detecting device for detecting radiation; a rotary device for rotating the radiation source; and a holder provided between the radiation source and the radiation detecting device that has two or more spaces for placing a subject. The holder includes space discriminating members for each of the spaces. Each of the space discriminating members has a unique sectional shape when cut along a plane where an imaginary circle exists. Here, the imaginary circle is a locus of rotation of the radiation source.