Medical observation device and lens barrel of medical observation device

The present disclosure provides a medical observation device to achieve improvement in functionality resulting from switching of optical elements and miniaturization of the device. The medical observation device includes: an imaging optical system configured to capture an image of a subject; an image sensor configured to photoelectrically convert the image of the subject captured by the imaging optical system; and an element holding frame configured to hold a plurality of optical elements and to be capable of being rotated around a rotation shaft. An axial direction of the rotation shaft is set to a direction orthogonal to an optical axis direction that is a direction of a line from the imaging optical system to the image sensor, and the element holding frame is rotated and thus at least one of the optical elements among the plurality of optical elements is positioned on an optical axis.