Provided is an occupant protection device which is disposed side by side with an under-cover of an instrument panel and has a harness connected to an inflator disposed on a front side of the under-cover in a vehicle traveling direction to protect a knee portion of an occupant, including a case having a side wall on which the harness is disposed, and a protrusion configured to extend from the side wall of the case toward a front of the under-cover in forward and backward direction of a vehicle, to come in contact with the under-cover, and to restrict movement of the under-cover to the front side in the forward and backward direction of the vehicle.