To provide a device and method for processing image by which the signal in a certain color space can be converted into the signal in another color space with high accuracy in a short time without preparing data for inverse conversion in advance.

When the input signal of a Lab color space is converted into the output of an RGA color space, a chrominance signal converting section 102 converts the given signal of the RGA color space into the signal of the Lab color space. A potential calculating section 103 extracts the difference between the input signal and the chrominance signal outputted from the converting section 102. An extremely small potential searching section 104 searches the signal which makes the extracted difference extremely small and is to be given to the converting section 102 and outputs the searched result as the converted chrominance signal of the RGB color space.