A safety device includes: a tool which performs a predetermined operation through an operation of an actuator; a mounting tool worn by a user operating the tool; a transmission unit which is provided in one of the tool or the mounting tool, and transmits a wireless signal in which a transmission direction is set to have high directional characteristic with respect to a certain direction; a reception unit which is provided in the other of the tool or the mounting tool, and receives the wireless signal transmitted by the transmission unit; and a controller which controls the tool on a condition that the reception unit recognizes the wireless signal.