A determination assist system for use in ultrasonic testing, adapted to generate a determination image used to determine whether or not a composite material component is healthy, based on data of plural kinds of test indices obtained in an ultrasonic testing device, the determination assist system characterized by: a first image generating section adapted to generate a first planar image which is a gradational image, based on data of signal intensity of a reflected sound wave as a first test index; a second image generating section adapted to generate a second planar image which is a gradational image, based on data of a propagation time of an ultrasonic sound wave as a second test index; a differentiation section adapted to differentiate the first planar image to generate a first differential image which is expressed as different tones corresponding to differential values, respectively, and differentiate the second planar image to generate a second differential image which is expressed as different tones corresponding to differential values, respectively; a binarization section which is adapted to binarize the first differential image to generate a first binary image including a first region in which a gradation is not less than a first threshold within the first differential image and a second region in which the gradation is less than the first threshold within the first differential image, and binarize the second differential image to generate a second binary image including a third region in which a gradation is not less than a second threshold within the second differential image and a fourth region in which the gradation is less than the second threshold within the second differential image; and a determination image generating section which is adapted to generate the determination image based on the first binary image and the second binary image, wherein the determination image generating section is configured to generate the determination image in such a manner that the first binary image and the second binary image are superposed together; and in the determination image, a region where the first region and the third region overlap with each other, a region where the first region and the fourth region overlap with each other, a region where the second region and the third region overlap with each other, and a region where the second region and the fourth region overlap with each other are identified such that the regions are distinguished from each other. a first image generating section adapted to generate a first planar image which is a gradational image, based on data of signal intensity of a reflected sound wave as a first test index; a second image generating section adapted to generate a second planar image which is a gradational image, based on data of a propagation time of an ultrasonic sound wave as a second test index; a differentiation section adapted to differentiate the first planar image to generate a first differential image which is expressed as different tones corresponding to differential values, respectively, and differentiate the second planar image to generate a second differential image which is expressed as different tones corresponding to differential values, respectively; a binarization section which is adapted to binarize the first differential image to generate a first binary image including a first region in which a gradation is not less than a first threshold within the first differential image and a second region in which the gradation is less than the first threshold within the first differential image, and binarize the second differential image to generate a second binary image including a third region in which a gradation is not less than a second threshold within the second differential image and a fourth region in which the gradation is less than the second threshold within the second differential image; and a determination image generating section which is adapted to generate the determination image based on the first binary image and the second binary image, wherein the determination image generating section is configured to generate the determination image in such a manner that the first binary image and the second binary image are superposed together; and in the determination image, a region where the first region and the third region overlap with each other, a region where the first region and the fourth region overlap with each other, a region where the second region and the third region overlap with each other, and a region where the second region and the fourth region overlap with each other are identified such that the regions are distinguished from each other.