There are provided an acoustic wave image generating apparatus and a control method thereof for making an insertion needle clear. A first ultrasound image is generated using ultrasound echo signals obtained from a first plurality of ultrasound transducers. From the first ultrasound image, an evaluation value indicating the discontinuity of a needle is calculated for an image of an insertion needle. In a case where the calculated evaluation value is less than a threshold value, a second ultrasound image is generated using ultrasound echo signals obtained from a second plurality of ultrasound transducers whose number is larger than the first plurality. The first ultrasound image is displayed if the evaluation value is equal to or greater than the threshold value, and the second ultrasound image is displayed if the evaluation value is less than the threshold value.