A portable ultrasound apparatus includes a sampler configured to obtain an in-phase signal and a quadrature signal from an ultrasound signal; a memory configured to store the in-phase signal and the quadrature signal and output the stored in-phase signal and the stored quadrature signal according to a first time delay; an interpolator configured to interpolate the in-phase signal and the quadrature signal outputted from the memory; and a phase rotator configured to apply a second time delay to the interpolated in-phase signal and the interpolated quadrature signal.