An ultrasound image forming method comprises a first step of receiving a first signal reflected from the object, a second step of obtaining an aberration correction value based on the first signal thus received, a third step of receiving a second signal reflected from the object when a second ultrasound corrected based on the aberration correction value is transmitted to the object, and a fourth step of forming an image from the aberration correction value and the second signal. The center frequency of the second ultrasound is between 0.5 MHz and 20 MHz, the center frequency of the first ultrasound is between 3/16 and 9/20 of the center frequency of the second ultrasound. By this method, an accurate aberration correction value can be obtained and an ultrasound imaging with high resolution can be achieved even if aberrations are large and difficult to correct.