To provide technique for converting a color space of an image signal.

A color space conversion circuit 110 converts a first signal corresponding to three elements which are the luminance, first color difference and second color difference constituting a first color space of a three-dimensional orthogonal coordinate system into a second signal corresponding to three elements which are the luminance, saturation and hue constituting a second color space of a three dimensional polar coordinate system. The color space conversion circuit 1 includes a saturation calculation unit 30 and a hue calculation unit 50, wherein the saturation calculation unit 30 includes a first multiplier 31 for outputting a first multiplication value as a multiplication value of first color differences, a second multiplier 32 for outputting a second multiplication value as a multiplication value of second color differences, an adder 33 for outputting an addition value of the first multiplication value and second multiplication value, and a square root extractor for outputting the square root of the addition value as a signal corresponding to the saturation, and the hue calculation unit 50 outputs a signal corresponding to the hue based upon the signal corresponding to the saturation and the signals corresponding to the first and second color differences.