An ultrasound image having a good image quality is generated in the neighborhood of a puncture needle without lowering the image quality of the whole ultrasound image. A first echo signal received by transmitting first ultrasonic waves focused on an imaging target position and a second echo signal received by transmitting second ultrasonic waves having the depth of the focal point positioned at a uniform position are obtained, the weights of the first echo signal and the second echo signal are determined according to the focal point positions of the respective ultrasonic waves, and weighted addition is performed to generate a corrected image.