An imaging apparatus for diagnosis and associated control method constructs multiple cross-sectional images in an axial direction inside the body lumen based on line data generated by radially operating a transmitting and receiving unit, and includes a receiving mechanism which receives a count value from a reference position of the transmitting and receiving unit, storage for storing the count value and the line data correlated with each other, an arrangement for constructing a longitudinal-sectional image by aligning the line data based on the count value, a display which displays the longitudinal-sectional image; and a mechanism which reads out line data correlated with the same count value as that of the line data disposed at the position appointed by the user on the displayed longitudinal-sectional image and reconstructing the cross-sectional image.