According to one embodiment, an ultrasonic diagnostic apparatus comprises an ultrasonic probe, an ultrasonic transmission/reception unit, an echo processing unit configured to generate complex data based on the echo signals, a phase shifting unit configured to shift a phase of each ensemble data constituted by N complex data associated with the same depth on the same ultrasonic raster in accordance with a reference phase, an interpolation processing unit configured to interpolate ensemble data associated with an interpolated raster between adjacent ultrasonic rasters based on the phase-shifted ensemble data, and an image data generation unit configured to generate image data based on the phase-shifted ensemble data and the interpolated ensemble data.