Airbag apparatus for motorcycles

An airbag apparatus for a motorcycle includes an airbag module with an airbag that is capable of being inflated and deployed so as to restrain the rider on a seat disposed behind the fuel tank from the front that is mounted on the vehicle body frame. Without requiring a modification of the configuration of the appearance constituting parts of the motorcycle, water, mud, or the like is prevented from breaking into the airbag module. The front portion of the seat that covers the airbag module to be mounted on the vehicle body frame at a position rearwardly of the fuel tank from above and extends to the position on the rear portion of the fuel tank is constructed so as to be opened with the rear side raised upwardly in response to inflation and deployment of the airbag.