To provide a vibration detecting device, an optical device, a camera system and an interchangeable lens capable of efficiently deciding whether the camera is in a fixed state or the camera is held by hand, and then, preventing a user from feeling unpleasant when the camera is held by hand and also when the camera is mounted on a tripod.

The device is provided with a supporting state deciding part 40 for deciding the supported state of the vibration correction camera based on a vibration detecting signal and then outputting the decision result, and the supporting state deciding part 40 is provided with a holding state detecting part 43 for detecting that the camera is supported by hand-holding and a fixed state detecting part 41 for detecting that the camera is fixed by a supporting member, and the supporting state is decided based on the detection result of the part 43 or the part 41.