1. An image processing apparatus capable of correcting gradation of image data formed from a brightness signal and a color signal sequentially superposed on the brightness signal in a time divisional relationship, comprising: characteristic amount detection means for successively detecting a characteristic amount indicative of a predetermined range neighboring to pixels of the image data; area discrimination means for discriminating areas to which the image data belong based on the characteristic amount and outputting discrimination results; coefficient calculation means for outputting correction coefficients to be used for correcting the pixel values of the image data based on the discrimination results; and correction means for correcting the pixel values of the image data using the correction coefficients, wherein the coefficient calculation means sets the correction coefficients at a fixed value when a signal level of the discrimination results is less than or equal to a prescribed value, and the coefficient calculation means sets the correction coefficients at a value less than the fixed value when the signal level of the discrimination results is greater than the prescribed value.