To reduce noise or the like generated at a boundary of tiles introduced in a video coding method. In a motion vector detection unit, a first tile video signal and a second tile video signal included in one picture are supplied to a first detection unit and a second detection unit, and a reference image is supplied from a frame memory to the first detection unit and the second detection unit. The first detection unit performs processing, by inter prediction, on the video signal positioned on or in the vicinity of a tile boundary between a first tile and another tile among many video signals included in the first tile. In this processing, the first detection unit generates a motion vector so as to preferentially refer to the reference image included in another tile different from the first tile among the reference images read out from the frame memory.