PROBLEM TO BE SOLVED: To provide an image diagnostic apparatus capable of performing correction with high accuracy and generating a combined image through properly adjusting the position of a top board.SOLUTION: A PET-CT apparatus includes: a top board height calculation unit 461 for calculating the height of a top board corresponding to a distance from the supporting point of the top board to an imaging position of an analyte from a correction table in which a distance from the supporting point of the top board to the imaging position, load of the analyte and the height of the top board at the imaging position are associated with one another and picked-up images obtained by continuous imaging a load estimation unit 462 for estimating a load of the analyte on the basis of the calculated height of the top board and the correction table a correction amount estimation unit 463 for estimating a height of the top board in imaging with a different imaging method on the basis of a distance from the supporting point of the top board to an imaging position where the analyte is imaged, the estimated load and the correction table and a corrected image generation unit 464 for correcting the height of the top board of the image picked up with the different imaging method to the estimated height and generating a picked-up image with the height of the top board corrected.
