To provide an occupant crash protection device at low cost capable of establishing a perfect protecting of an occupant.

The occupant crash protection device is equipped with a protecting space part 153 for relieving the restraining pressure at the time of restraining the occupant in the central region of an air bag 150 in order to restrain the occupant on the front passenger seat S irrespective of his physique at the time of spreading and inflating, and judgement is made whether the object lying directly on the seat S is the occupant 10 or a child seat 12 on the basis of the tension information given by a belt tension sensor 114, and if the object lying is the occupant 10, an inflator 140 is controlled so that the space part 153 of the air bag 150 spreads and inflates in the condition that the restraining pressure to the occupant 10 is relieved. If the judgement is such that the object lying is child seat 12, the inflator 140 is controlled so as to suppress the influence of the restraining pressure of the air bag 150 to the occupant on the child seat 12.