An ultrasound diagnostic apparatus, comprising: a data acquisition section which performs transmission and reception of ultra-sound with respect to a three-dimensional space including an object tissue to acquire volume data; a representative cross section processing section which, when a plurality of manual tracing lines are formed on a plurality of representative cross sections (58, 60) which are set with regard to the object tissue, applies a first correction processing to each manual tracing line; a non-representative cross section processing section which forms, by interpolation processing based on a plurality of manual tracing lines to which the first correction processing has been applied, a plurality of interpolation tracing lines on a plurality of non-representative cross sections (58, 60) which are set with regard to the object tissue, and applies a second correction processing to each interpolation tracing line; and a unit which extracts object tissue data from the volume data or calculates a volume of the object tissue, based on rows of tracing lines formed of a plurality of manual tracing lines to which the first correction processing has been applied and a plurality of interpolation tracing lines to which the second correction processing has been applied characterized in that the first correction processing includes partially correction processing in which a portion of each manual tracing line is corrected based on an actual tissue outline and another portion of the manual tracing line is maintained, the representative cross section processing section includes: a selection section which selects the plurality of representative cross sections (58, 60) from a set of cross sections which is set with respect to the object tissue; a unit which receives a tracing input from a user with respect to each representative cross section (58, 60) which is selected; and a first correction processing section which, for the first correction processing, determines whether or not correction can be applied for each point on each manual tracing line and corrects a position of a point which is determined to be correctable based on an actual tissue outline, wherein the first correction processing section determines whether or not correction can be performed by setting a cross line with regard to each point and performing edge detection on the cross line, wherein if an edge is detected it is determined that an correction can be performed and if no edge is detected it is determined that no correction can be performed. a data acquisition section which performs transmission and reception of ultra-sound with respect to a three-dimensional space including an object tissue to acquire volume data; a representative cross section processing section which, when a plurality of manual tracing lines are formed on a plurality of representative cross sections (58, 60) which are set with regard to the object tissue, applies a first correction processing to each manual tracing line; a non-representative cross section processing section which forms, by interpolation processing based on a plurality of manual tracing lines to which the first correction processing has been applied, a plurality of interpolation tracing lines on a plurality of non-representative cross sections (58, 60) which are set with regard to the object tissue, and applies a second correction processing to each interpolation tracing line; and a unit which extracts object tissue data from the volume data or calculates a volume of the object tissue, based on rows of tracing lines formed of a plurality of manual tracing lines to which the first correction processing has been applied and a plurality of interpolation tracing lines to which the second correction processing has been applied a selection section which selects the plurality of representative cross sections (58, 60) from a set of cross sections which is set with respect to the object tissue; a unit which receives a tracing input from a user with respect to each representative cross section (58, 60) which is selected; and a first correction processing section which, for the first correction processing, determines whether or not correction can be applied for each point on each manual tracing line and corrects a position of a point which is determined to be correctable based on an actual tissue outline,