A medical stereoscopic observation device comprising: an acquisition section that acquires input image data of a partial region of a patient's body; a parallax control section that controls, for each of a plurality of different display regions, a parallax value in accordance with display size of the display region and parameters related to an imaging state, the parameters related to the imaging state comprising a distance between respective optical axes of imaging sections of an imaging unit which image an imaging target from different respective viewpoints to generate the input image data and a distance between the imaging unit and the imaging target; and an image generation section that generates, for each display region, a parallax image corresponding to each of a plurality of viewpoints for display in the display region, on a basis of the acquired input image data and the parallax value corresponding to the display region, wherein the parallax control section controls, for each of a plurality of display regions presented on a common display section, the parallax value in accordance with display size in the display region and controls the parallax value corresponding to the display region in accordance with a change of the display size of the display region, and the image generation section generates, for display in each of the plurality of display regions, the parallax image corresponding to each of a plurality of viewpoints, on a basis of the parallax value corresponding to the display region and updates the parallax image for display in the display region on a basis of a control result of the parallax value; wherein two of the display regions are of different sizes; and the imaging generation section is configured to exchange the parallax images displayed in each of the display regions of different sizes, the parallax values of the exchanged parallax images being controlled in accordance with the display sizes of the parallax images after the exchange. an acquisition section that acquires input image data of a partial region of a patient's body; a parallax control section that controls, for each of a plurality of different display regions, a parallax value in accordance with display size of the display region and parameters related to an imaging state, the parameters related to the imaging state comprising a distance between respective optical axes of imaging sections of an imaging unit which image an imaging target from different respective viewpoints to generate the input image data and a distance between the imaging unit and the imaging target; and an image generation section that generates, for each display region, a parallax image corresponding to each of a plurality of viewpoints for display in the display region, on a basis of the acquired input image data and the parallax value corresponding to the display region, wherein the parallax control section controls, for each of a plurality of display regions presented on a common display section, the parallax value in accordance with display size in the display region and controls the parallax value corresponding to the display region in accordance with a change of the display size of the display region, and the image generation section generates, for display in each of the plurality of display regions, the parallax image corresponding to each of a plurality of viewpoints, on a basis of the parallax value corresponding to the display region and updates the parallax image for display in the display region on a basis of a control result of the parallax value; wherein two of the display regions are of different sizes; and the imaging generation section is configured to exchange the parallax images displayed in each of the display regions of different sizes, the parallax values of the exchanged parallax images being controlled in accordance with the display sizes of the parallax images after the exchange. <EOS>