MONITORING DEVICE

A monitoring device includes an in-vehicle mount and a stationary mount as mounts to and from which an imaging unit configured to take a video is able to be attached and detached. The imaging unit is configured to automatically switch the operation mode according to the mount on which the imaging unit is mounted in such a manner that the imaging unit operates in the in-vehicle operation mode when the imaging unit is mounted on the in-vehicle mount, and operates in the stationary operation mode when the imaging unit is mounted on the stationary mount.