1. A tomographic image generating system comprising: an imaging member that includes a radiation source for emitting radiation to a subject, a radiation detector including a two-dimensional array of radiation detecting elements each detecting the radiation to generate an electrical signal, the radiation detector acquiring a projected image in proportion to the emitted radiation, and a subject table for holding the subject, the subject table being disposed between the radiation source and the radiation detector, and that captures the projected image a predetermined number of times while changing a positional relationship between the radiation source and the radiation detector; a reconstructing member that generates a tomographic image of the subject from the projected image captured by the imaging member; an acquiring member that acquires a thickness of the subject and/or a two-dimensional shape of a surface of the subject, the surface of the subject being irradiated with radiation; and a controlling member that determines an imaging condition for the imaging member and/or a reconstructing condition for the reconstructing member generating the tomographic image of the subject, on the basis of the thickness and/or the two-dimensional shape of the subject acquired by the acquiring member.