An image processing device is an image processing device configured to cause a display to display three-dimensional data as a three-dimensional image, the three-dimensional data representing a biological tissue. The image processing device includes: a control unit configured to detect a series of positions of a catheter inserted into the biological tissue from data obtained in time series by a sensor observing the surrounding of a lumen of the biological tissue while moving in the lumen, and to switch a display mode between a first mode for displaying a first figure representing the series of positions in the three-dimensional image, and a second mode for displaying a second figure representing one position among the series of positions in the three-dimensional image.