[Problem] To provide a diagnostic imaging device and a method of operation that make it possible to reduce the workload on a practitioner and an operator that are required to check the state of use of a medical apparatus that has been inserted into a lumen of the body. [Solution] A diagnostic imaging device (10) comprises: a diagnostic imaging catheter (100) provided with a sheath (110) that can be inserted into the body, an imaging shaft (140) that can be moved back and forth along an axial direction of the sheath and that has, provided at a distal end part thereof, an imaging unit (145) for acquiring a tomographic image of a lumen of the body, and a hub (160) arranged on a proximal end side of the sheath (110)； a drive device (200) that can be connected to the hub of the diagnostic imaging catheter and that drives the movement back and forth of the imaging shaft； and a control unit (300) for controlling operation of the drive device and the imaging unit. The control unit implements a reciprocating motion mode for causing the imaging unit to retract at least once and to advance at least once between an advance limit position (De) and a retraction limit position (Pe) in the axial direction. The control unit, in the reciprocating motion mode, implements a first display control for causing a display device (400) to display, synchronously with retraction of the imaging unit, a first tomographic image (511) acquired while the imaging unit was retracting, and implements a second display control for causing the display device to display, synchronously with advancing of the imaging unit, a second tomographic image (512) acquired while the imaging unit was advancing. The control unit implements, if the first display control is implemented, a first reporting operation for reporting that the imaging unit is retracting while the imaging unit is retracting, and implements, if the second display control is implemented, a second reporting operation for reporting that the imaging
