An ultrasound diagnosis apparatus capable of extracting an object tissue within a living body with high precision is provided. A row of reference cross sections is set with regard to volume data. The row of reference cross sections includes a plurality of manual tracing reference cross sections and the remaining sections, i.e. a plurality of automatic tracing reference cross sections. With regard to the manual tracing reference cross sections, manual tracing processing and automatic correction processing is applied. With regard to the automatic tracing reference cross sections, automatic generation processing and automatic correction processing for interpolation tracing lines is applied. Finally, the object tissue is extracted or the volume thereof is calculated based on a plurality of tracing lines. When the similarity between shapes of adjacent manual tracing lines is small, one or a plurality of manual tracing lines may be additionally provided between these tracing lines.