1. An ultrasonic diagnosis apparatus comprising: an ultrasonic probe; a transmission/reception circuit configured to transmit an ultrasonic wave to a subject via the ultrasonic probe and receive an echo signal corresponding to an ultrasonic wave reflected by the subject; and processing circuit configured to generate first volume data based on the received echo signal; generate low-frequency volume data and high-frequency volume data on spatial frequencies based on the generated first volume data; calculate three eigenvalues, identify three-dimensional structure patterns of three-dimensional structures indicating a degree of anisotropic structure components and isotropic structure components contained in the generated low-frequency volume data using the three eigenvalues, calculate edge information in accordance with the identified structure patterns using two eigenvalues of the three eigenvalues, and apply a nonlinear anisotropic diffusion filter having a filter characteristic corresponding to the calculated edge information to the low-frequency volume data; perform edge enhancement processing for the high-frequency volume data using the generated edge information; and generate second volume data with reduced speckle and reduced noise based on the low-frequency volume data to which the nonlinear anisotropic diffusion filter is applied and the high-frequency volume data for which edge enhancement processing is performed.