An X-ray CT apparatus is provided with an X-ray tube electric current modulation pattern calculation means that calculates an X-ray tube electric current modulation pattern based on a three-dimensional model of an examinee calculated on the basis of a scanogram image of the examinee, a starting-up shape acquisition means that acquires a starting-up shape of CT values of a predetermined portion of the examinee or CT value time differences, a time contrast curve estimate means that estimates a time contrast curve indicative of a time sequential change of contrast in a diagnostic portion of the examinee at each slice position at a scan time based on the acquired starting-up shape of the CT values or CT value time differences, an examinee three-dimensional model modification means that modifies the three-dimensional model of the examinee based on the estimated time contrast curve, and an X-ray tube electric current modulation pattern modification means that modifies the X-ray tube electric current modulation pattern based on the modified three-dimensional model of the examinee.
X-RAY CT APPARATUS