A safety device for a juice extractor includes a switch unit connected to an outside of the feed channel and electrically connected to a power source of the motor. A collar is movably mounted to the feed channel and includes an insertion which is inserted into an opening in a handle of the juice extractor so as to activate the switch unit to drive the motor and the blade disc. When the collar is moved away from the handle, the insertion is removed from the switch such that the motor and the blade disc are stopped to ensure the safety for the users.