1. An X-ray CT apparatus comprised with an X-ray generating means, an X-ray detector disposed opposing to the X-ray generating means, a rotating means for rotating the X-ray generating means and the X-ray detector on a circular orbit of a same rotation center, a control means for controlling so as to irradiate X-rays from the X-ray generating means to an object to be examined laid along the rotation center and to detect by the X-ray detector X-ray dose penetrated through the object while rotating the X-ray generating means and the X-ray detector through the rotating means and a reconstruction computing means for performing reconstruction computation by making use of the data of the penetrated X-ray dose obtained under the control of the control means and acquiring a tomographic image, characterized in that the X-ray CT apparatus is further being provided with an input means being inputted of information with respect to an target tissue of the object to be discriminated in the tomographic image and of an index with respect to correctness of the discrimination, and a scanning condition determining means for determining scanning conditions for discriminating the target tissue based on the index inputted by the inputting means.