Alignment of an ultrasonograph and volume data obtained beforehand is correctly performed without requiring a user to perform complicated operation. First volume data for an ultrasonograph and second volume data obtained by another imaging apparatus are received and aligned. A predetermined imaging part selected from a plurality of imaging parts of a subject is received from a user. The second volume data are initially rotated by a rotation angle corresponding to the imaging part received by the receptor, and alignment of the initially rotated second volume data and the first volume data after is further carried out.