The vehicle airbag device includes an airbag module, an airbag lid member, and a reinforcing member. The reinforcing member includes at least an attachment flange part having a fixing part such as a welding part and a module accommodation part. The attachment flange part is provided with a module fixing part, the module fixing part being protruded from an under surface of the attachment flange. The module fixing part is provided with, at a lower end thereof, a fragile part that is broken by a force smaller than a welding force (fixing force) of the welding part and a separation prevention part that keeps connecting a portion below the fragile part to the module fixing part when the fragile part is broken.