A method capable of acquiring data at a high speed while holding proper precision during measurement with an infrared imaging apparatus uses an FTIR device of a continuous scan type for detecting a signal by a multi-element detector. A method which acquires data from a multi-element detector in an infrared imaging apparatus. The method involves starting to scan an element of the said multi-element detector synchronously with a sampling signal based on a reference signal of an interferometer, and scanning the element at a higher frequency than a sampling frequency of the sampling signal. The method further involves completing the scanning of all the elements before a next sampling signal to the sampling signal starting the element scanning is generated, and repeating a series of operations every time the sampling signal is generated.