There is provided an occupant protection device for a vehicle, the occupant protection device including a side collision prediction device configured to predict a collision with a side of a host vehicle and output a prediction result including determination about whether or not the predicted collision is an inevitable collision, a physical quantity detection device configured to detect a physical quantity related to the collision with the side of the host vehicle and output a detection value of the physical quantity, an airbag device configured to expand to protect an occupant of the vehicle when the airbag device is operated, and an electronic control unit.