A flexible video cadence detecting apparatus includes a motion detecting unit, a cycle detecting unit, a film detecting unit, and a de-interlacing unit. The motion detecting unit receives a plurality of continuous field images and determines whether or not there is motion in each field image. The motion detecting unit assigns a first or a second value according to whether or not there is motion in the field image, so as to obtain a value stream. The cycle detecting unit receives the value stream and detects whether or not the first or the second value has a cycle, so as to output a cycle determinant. The film detecting unit receives the value stream and the cycle determinant and determines whether or not the field images are a film, to output a cadence pattern. The de-interlacing unit restores the field images into an original film according to the cadence pattern.