PURPOSE: To share the constitution of an A/D conversion device and to perform processing for two luminance/color difference signals by providing a switching circuit for time division multiplexing of two color difference signals before performing an AD conversion for chroma out of AD conversions of luminance/chroma signal.

CONSTITUTION: The A/D conversion device is provided with a switching circuit 32 switching color difference signals 30, 31 and generating a color difference signal 33 for which a time division multiplexing is performed, a circuit 34 switching the color difference signal 33 and a chroma signal 14 and a circuit 35 switching the color difference signal to color difference signals 36, 37. The band of the chroma signal 14 is fsc=3.58MHz and an A/D converter is sampled at 2 fsc. The color difference signals 30, 31 are generally the signals having the band of 0.5 to 1.5MHz, and the time division multiplexing and the A/D conversion become possible for the signal. The two color difference signals for which the time division are performed are the same signal as output signals 17, 18 of a color demodulation circuit 6 and are capable of dealing with a rear step processing commonly after being switched in a switching circuit 38 by interposing a switching circuit 35 converting the color difference signal for which the time division multiplexing is performed to the color difference signals 36, 37.