PURPOSE: To facilitate separation of an outer door by sectioning the outer door to be provided on an interior trim material by a coating having explosive provided along a specified pattern, in a device in which an air bag device is arranged on the back side of the interior trim material.

CONSTITUTION: An air bag device for a front passenger seat, to be housed in a right part of an installment panel 16 is housed in a housing part 18 provided on the back of an interior trim material in the folded state. When a vehicle collides and an air bag is inflated, the air bag is developed in a seat section 12 with releasing of one or more outer doors 28A, 28B formed on the trim material in which the housing part 18 is provided on the back. In this case, in order to enable releasing (breaking) of respective doors 28A, 28B, a coating 30 having explosive causing partial or whole deterioration of the outer layer of a skin layer 32 of the installment panel 16 is provided by a pattern for forming three side parts of respective doors 28A, 28B.