1. An image processing device comprising: a plurality of isolated-point candidate detection sections, each being configured to calculate a parameter value used for detecting an isolated-point candidate in a color image signal in a first color space; and an isolated-point degree determination section configured to determine an isolated-point degree of a target pixel on the basis of parameter values calculated by the plurality of isolated-point candidate detection sections, wherein: one of the plurality of isolated-point candidate detection sections calculates a first parameter value with respect to the target pixel of the color image signal based on at least a difference between a pixel value of the target pixel and a pixel value of a peripheral pixel of the target pixel, at least one of the plurality of isolated-point candidate detection sections is provided with a color-space conversion section configured to color-convert a first plurality of color signals constituting the color image signal in the first color space, into a second plurality of color signals in a second color space, and calculates a second parameter value with respect to the target pixel based on at least a difference between a pixel value of one of the second plurality of color signals, corresponding to the target pixel, and a pixel value of another one of the second plurality; and the isolated-point degree determination section determines the isolated-point degree of the target pixel on the basis of the first parameter value, and at least one of the second parameter values.