Abstract: A sensing device for a safety belt comprising a tightening unit having a fastening plate; a pulling force recording unit fastening seat of the safety belt; an impact status recording unit; a record indication unit; and a cartridge housing containing these units therein, wherein the pulling force recording unit comprises a clipping frame containing a fastening rim with one end protruded out therefore, and an engaging element capable of changing the resistance value when a pulling force is exerted, the impact status recording unit comprises a pendulum, on a circuit board, which changes the resistance value of the circuit board by the swinging of the pendulum, and the fastening status recording unit comprises an enumerating sensing switch, and the electrical signal and resistance of the units are transferred to the record indication unit.