Abstract: An occupant protection device includes a first sensor configured to output vehicle information indicating a traveling state of a vehicle and a situation around the vehicle, a second sensor configured to output occupant information indicating a seating state of an occupant, a stimulus application unit that is to be worn by the occupant and is configured to apply a stimulus to the occupant, and a controller configured to control the stimulus application unit. The controller predicts an impact to be received by the vehicle, determines a stimulus application content by the stimulus application unit necessary for correcting a posture of the occupant to a posture prepared for the impact when the impact is predicted, and activates the stimulus application unit in accordance with the determined stimulus application content and thus corrects the posture of the occupant prior to a timing when the vehicle receives the impact.