A living tissue region determining unit of a gain correction data generating section determines a diagnostic living tissue region on the basis of an S/N and a dispersion value of ultrasound data collected from each of a plurality of slice sections in a gain correction scan mode intended for the generation of gain correction data for volume data. A gain correction map generating unit applies a least squares method to the average value of the ultrasound data in a plurality of regions set by dividing the living tissue region into predetermined sizes, thereby generating two-dimensional gain correction maps. Then, an interpolating processing unit interpolates, in a slice direction, the gain correction map generated for each of the plurality of slice sections, and generates three-dimensional gain correction data corresponding to each voxel of the volume data.