A valve drive device comprising a valve body drive mechanism including a drive gear, a driven gear for turning the valve body, and a power transmission switching part provided with a protruded part of the drive gear and a turning restriction part turnably attached to the driven gear. The turning restriction part comprises a lever part urged with an urging force toward an outer side of the driven gear. The driven gear comprises a lever turning restriction part for restricting turning of the lever part and the lever part is structured to perform a contact operation with the protruded part and a separating operation separated from a contact position with the lever turning restriction part. The valve body drive mechanism further comprises a foreign matter entry restraining part which covers at least a part of a region formed between the lever part and the lever turning restriction part.