An image processing device and a deinterlacing process thereof are provided. The deinterlacing process reads a memory to retrieve ten pixels of an image field that are temporarily stored in the memory, wherein the ten pixels are located on a first column, a second column, a third column, a fourth column and a fifth column of a first row and a second row of the image filed. Then, the deinterlacing process estimates the data of an interpolated pixel according to the data of the ten pixels. The interpolated pixel is inserted between the first and second rows of the image field on the third column to form a deinterlaced image frame.