An image processing apparatus comprising: an image acquisition unit that acquires an endoscopic image formed by an image signal including a narrow-band image signal; a color information calculation unit that calculates brightness, hue, and saturation of each pixel of the endoscopic image; a first color difference expansion unit that changes the hue of each pixel of the endoscopic image such that a difference between a changed hue and the hue of a reference color indicating a normal part is more than a difference between an original hue and the hue of the reference color in a case in which a difference between the hue of the reference color and the hue of the pixel is within a first range and changes the hue of the pixel to the original hue in a case in which the hue of each pixel is matched with the hue of the reference color and a case in which the hue difference is beyond the first range; a second color difference expansion unit that changes the saturation of each pixel such that a difference between a changed saturation and the saturation of the reference color which is determined according to the brightness of each pixel of the endoscopic image is more than a difference between an original saturation and the saturation of the reference color in a case in which a difference between the saturation of the reference color and the saturation of the pixel is within a second range and changes the saturation of the pixel to the original saturation in a case in which the saturation of each pixel is matched with the saturation of the reference color and a case in which the saturation difference is beyond the second range; and an output unit (66, 88) that outputs an endoscopic image in which the brightness of each pixel is the original brightness and whose color has been changed to a color having the hue obtained by the first color difference expansion unit and the saturation obtained by the second color difference expansion unit. an image acquisition unit that acquires an endoscopic image formed by an image signal including a narrow-band image signal; a color information calculation unit that calculates brightness, hue, and saturation of each pixel of the endoscopic image; a first color difference expansion unit that changes the hue of each pixel of the endoscopic image such that a difference between a changed hue and the hue of a reference color indicating a normal part is more than a difference between an original hue and the hue of the reference color in a case in which a difference between the hue of the reference color and the hue of the pixel is within a first range and changes the hue of the pixel to the original hue in a case in which the hue of each pixel is matched with the hue of the reference color and a case in which the hue difference is beyond the first range; a second color difference expansion unit that changes the saturation of each pixel such that a difference between a changed saturation and the saturation of the reference color which is determined according to the brightness of each pixel of the endoscopic image is more than a difference between an original saturation and the saturation of the reference color in a case in which a difference between the saturation of the reference color and the saturation of the pixel is within a second range and changes the saturation of the pixel to the original saturation in a case in which the saturation of each pixel is matched with the saturation of the reference color and a case in which the saturation difference is beyond the second range; and an output unit (66, 88) that outputs an endoscopic image in which the brightness of each pixel is the original brightness and whose color has been changed to a color having the hue obtained by the first color difference expansion unit and the saturation obtained by the second color difference expansion unit.