Provided are a CT-image processing apparatus and a method which can remove noise caused by one of a heartbeat and a breathing beat and extract only an accurate periodic motion by the other one. A CT-image processing apparatus 5 that processes projection data in which an animal is captured as a subject at each time by an X-ray CT apparatus includes a breathing beat threshold specification unit 36a to specify a lower limit of a breathing beat frequency from a feature amount waveform within a ROI for breathing beat synchronization in a series of projection data, a heartbeat threshold specification unit 37a to specify a lower limit of a heartbeat frequency from a feature amount waveform within a ROI for heartbeat synchronization in the series of projection data, a breathing beat extraction unit 36b to extract a breathing beat waveform using a band-pass filter defined by the lower limit of the breathing beat frequency and the lower limit of the heartbeat frequency.
