1. A radiotomography apparatus, comprising: a radiation detection device that irradiates radiation from a radiation source in multiple directions around an object to be examined and detects radiation that is transmitted through the object from the multiple directions; a table on which the object lies and which can move the object in a body axis direction of the object; a reconstruction parameter setting device that sets reconstruction parameters that include an amount of movement of the table in the body axis direction, and that are used to reconstruct an image of the object; a reconstruction view area calculating device that calculates a reconstruction view area for at least one data segment that is necessary for a reconstruction calculation that is determined for each spatial position that is reconstructed based on the reconstruction parameters; a reference segment position setting device that sets a reference segment position in the calculated reconstruction view area according to a phase signal that is obtained by dynamic analysis of the object; an effective segment calculating device that calculates a data segment including the set reference segment position as an effective segment using a predetermined weight function, said effective segment calculating device including number of effective segments calculating device that calculates a number of effective segments for which the set reference segment position is present in the reconstruction view area, a segment width calculating device that calculates a width of an effective segment that is defined at the reference segment position for each of the calculated number of effective segments, using an area which an adjacent data segment thereof has, and a weight function calculating device that calculates said weight function which highly contributes to image reconstruction of data segments for which the phase signals are equal by widths of the calculated effective segments and the set reference segment positions, and for which the sum of weights of data segments that face the effective segments are equal; and an image creating device that creates an image by reconstructing the calculated effective segments.