A passive hood hinge for a vehicle includes a hinge bracket fixedly mounted to a body of the vehicle, a hinge arm connected to a hood and rotatable when opening or closing the hood, a lowering link pin inserted into a guide slot formed at a rear end of the hinge bracket, a lowering link having a middle portion hinged to the lowering link pin and a rear end hinged to the rear end of the hinge arm, a transfer link having front/rear ends respectively hinged to front end of the hinge bracket and rear end of the hinge arm, and a locking means that restricts the lowering link pin to be located in an upper region of the guide slot during ordinary operations, and allows the lowering link pin to be lowered toward a lower region of the guide slot when a hood panel is deformed by a collision.