A device 1 is an OCT device that splits a low-coherence light L0 into a signal light LS and a reference light LR, detects an interference light LC obtained by superimposing the signal light LS propagated through an eye E and the reference light LR propagated through a reference mirror 174, and forms an image of an fundus oculi Ef. The device 1 has a scan unit 141 that scans the eye E with the signal light LS. When a cross-section position is designated in an fundus oculi image Ef, the device 1 repetitively scans with the signal light LS along each cross-section position to repeatedly forms tomographic images at each cross-section position, thereby displaying a tomographic motion image at each cross-section position on a display 240A. An operator can observe the tomographic motion image to designate the range and timing for measurement of a tomographic still image.
