A charger with a replaceable signal for a car includes a casing and a circuit board. The casing is provided with a current taking plug at a lateral side thereof. The circuit board is disposed in the casing and electrically connected to the current taking plug for rectifying and transformed an input power. It is characterized in that the casing at a proper position thereof is provided with a signal socket to electrically connect with the circuit board and a stopper being located therein; a signal line at an end thereof has a signal plug being detachably inserted into the signal socket and the stopper has an engaging piece for engaging with the signal plug and allowing the signal line fixedly joined to the casing laterally and the signal line at a another end thereof has a connector. Once the connector of the signal line is connected to an output/input port of a personal electric product and the current taking plug is inserted to a lighter device in a car, a recharging circuit can be performed.