There are provided an ultrasound image generating apparatus, which generates a high-quality ultrasound image even in a deep portion of a subject, and a control method thereof. In an ultrasound image (Img), for a portion (Ar1) equal to or less than a depth threshold value (D1), a real scanning line (L1) obtained from an acoustic wave echo signal is used. In the ultrasound image (Img), for a portion (Ar2) deeper than the depth threshold value (D1), an interpolation scanning line (L2) located between the real scanning lines (L1) is generated from an acoustic wave echo signal having a positional deviation between a focusing position of ultrasound waves and an observation target position. Also for a portion deeper than the interpolation scanning line (L2), a high-quality ultrasound image (Img) is obtained.