To eliminate: (windmill windmill)-like artifacts Windmill that when performing a helical scan to X-ray CT, have occurred inevitably. Therefore, X-ray CT apparatus of the present invention, X-ray detector the X-ray source (12) has a plurality of detection elements arranged two-dimensionally, is arranged so as to face each other across the axis of rotation of the desired on the projection data, projection data for two-dimensional obtained based on the X-ray detection data detected by the detecting element while rotating around the rotation center axis (13), X-ray source (13) and a (25) reconstruction means for reconstructing an image by performing the operation along different paths for the (Z-axis direction), and back projection direction along the rotation center axis of the X-ray path.X線CTでへリカルスキャンを行なうに際し、不可避的に発生しているウィンドミル(windmill:風車)状アーチファクトを解消する。そのため、本発明のX線CT装置は、X線源(12)と、二次元配列された複数の検出素子を有し、所望の回転中心軸を挟んで対向して配置されたX線検出器(13)と、X線源(13)を前記回転中心軸の回りに回転させながら前記検出素子で検出されたX線検出データを基に得られる二次元的な投影データを、当該投影データに関するX線経路とは前記回転中心軸に沿う方向(Z軸方向)について異なる経路に沿って、逆投影する演算を施して画像を再構成する再構成手段(25)とを備える。
