An image processing apparatus comprising: an image acquiring unit for acquiring an image of a body part captured by an imaging device; and a determining unit for determining, in a case where there is a region where luminance is saturated in the acquired image, a cause of the saturation of the luminance based on a distribution of the luminance in the acquired image, wherein the determining unit is arranged to: determine, when the region where the luminance is saturated includes a central portion in the image, the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance, determine, when the region where the luminance is saturated includes a peripheral portion in the image, the cause of the saturation of the luminance is external light, and notify the image acquiring unit of the cause of the saturation of the luminance, and wherein the image acquiring unit is arranged to acquire another image of the body part again after: outputting information for increasing the distance from the imaging device to the body part, in a case where the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance; or changing imaging conditions of the imaging device, in a case where the cause of the saturation of the luminance is an influence of external light. an image acquiring unit for acquiring an image of a body part captured by an imaging device; and a determining unit for determining, in a case where there is a region where luminance is saturated in the acquired image, a cause of the saturation of the luminance based on a distribution of the luminance in the acquired image, wherein the determining unit is arranged to: determine, when the region where the luminance is saturated includes a central portion in the image, the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance, determine, when the region where the luminance is saturated includes a peripheral portion in the image, the cause of the saturation of the luminance is external light, and notify the image acquiring unit of the cause of the saturation of the luminance, and determine, when the region where the luminance is saturated includes a central portion in the image, the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance, determine, when the region where the luminance is saturated includes a peripheral portion in the image, the cause of the saturation of the luminance is external light, and notify the image acquiring unit of the cause of the saturation of the luminance, and wherein the image acquiring unit is arranged to acquire another image of the body part again after: outputting information for increasing the distance from the imaging device to the body part, in a case where the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance; or changing imaging conditions of the imaging device, in a case where the cause of the saturation of the luminance is an influence of external light. outputting information for increasing the distance from the imaging device to the body part, in a case where the cause of the saturation of the luminance is the distance between the imaging device and the body part being shorter than a predetermined distance; or changing imaging conditions of the imaging device, in a case where the cause of the saturation of the luminance is an influence of external light.