An image processing device has a storage unit, a read-out unit, a color information generating unit, a color information converting unit and a color replacing unit. The storage unit stores color information of spot colors. The read-out unit reads out the color information from the storage unit. The color information generating unit generates color information of an alternate color based on the color information of the spot color. The color information converting unit generates each of first and second color information, the first color information is generated by converting the color information of the color plate for which color replacement is instructed into the color information of the spot color, the second color information is generated by converting the color information of the color plate for which the color replacement is instructed into the color information of the alternate color. The color replacing unit generates new color information.