A seismic imaging technology, and more specifically, an imaging technology for modelling a subsurface structure by updating a velocity model of each frequency band in the ascending, descending order or any random order of frequencyThe purpose of the present disclosure is to directly compute the difference between the velocity of the actual subsurface velocity and an initial guess of the velocity.According to one aspect of the present invention, a seismic imaging apparatus for performing iterative application of the direct waveform inversion to image a subsurface structure of an area to be measured may include a waveform inverter to update a reference velocity model while changing a frequency band in a set order, by using parameter perturbation that is obtained from a virtual scattering source and an updated reference wavefield.