A seat cushion airbag for a vehicle includes an airbag cushion that is formed with a center part installed in a center of or around a front part of a seat cushion of a vehicle and is located between legs of a passenger when being deployed. An extension part extends on both sides of the center part and is located above the legs of the passenger and an inflator is connected to the airbag cushion and provides an expansion force to the airbag cushion.