An occupant protection device includes: a controller; first and second bus lines; a first collision sensor arranged on a side of the vehicle, and transmitting a first signal to the controller via the first bus line; a second collision sensor arranged on a center of the vehicle, and transmitting a second signal to the controller via the second bus line; and a third collision sensor arranged on a front side from the first collision sensor, and transmitting a third signal to the controller via the second bus line. The controller determines the collision on the side of the vehicle based on the first and second signals. The controller determines the collision on a part of the vehicle based on the third signal, the part disposed on the front side from the first collision sensor. The controller activates an occupant protection element.