Abstract: An operation device according to the present invention includes: a rotation operation unit that is rotatable about a rotation axis and is installed so that an operation site formed on a rotation surface is exposed outside through an opening formed in an operation panel; and a support unit that covers at least part of a separated site of the rotation operation unit located away from the operation site along a rotation axis direction and has a sliding site coming into contact with part of the separated site and slidably supporting rotation of the rotation operation unit. Then, the support unit is configured to form a space part retaining grease applied to the rotation operation unit between the support unit and the separated site located on a side opposite to the operation site of the rotation operation unit with reference to the sliding site.