A method and apparatus for obtaining a dynamic radiographic image with enhanced resolution, in which an electrocardiogram of a subject is obtained, and five time phases are allocated to each cardiac beat period (1 second). The initial X-ray irradiation is performed at 1st time phase of 1st beat to obtain a radiographic image. Thereafter, X-ray irradiations are performed sequentially at 2nd time phase of 2nd beat, at 3rd time phase of 3rd beat, at 4th time phase of 4th beat, and at 5th time phase of 5th beat to obtain respective radiographic images. The five radiographic images obtained are combined at the time interval of 0.2 seconds to be displayed as a motion image. The time interval between the irradiations of the X-ray is 1.2 seconds, so that image signals corresponding to 1st to 5th time phases may be obtained with high resolution.