1. An information calculation device which calculates information relating to a traveling lane where a vehicle travels based on a captured image in front of the vehicle captured by a monocular camera mounted in the vehicle, the information calculation device comprising: an electronic control unit configure to i) detect edge points in the captured image, ii) specify left lane marker candidate points as the edge points of a lane marker on a left side of the vehicle in the traveling lane and right lane marker candidate points as the edge points of a lane marker on a right side of the vehicle in the traveling lane based on the edge points, and iii) calculate a lateral position of the vehicle in the traveling lane, a pitch angle of the vehicle with respect to the traveling lane, a yaw angle of the vehicle with respect to the traveling lane, a lane width of the traveling lane, a curvature of the traveling lane in front of the vehicle, and a curvature change rate as a rate of change of the curvature based on the right lane marker candidate points and the left lane marker candidate points by Kalman filter processing determined in advance when two edge points satisfying separation conditions set in advance are included in each of the right lane marker candidate points and the left lane marker candidate points, the electronic control unit being configured to, in response to the two edge points satisfying the separation conditions being included in one of the right lane marker candidate points and the left lane marker candidate points and no edge point is included in the other one of the right lane marker candidate points and the left lane marker candidate points, set the pitch angle of the vehicle to zero and to set the lane width of the traveling lane to a predetermined value and to calculate the lateral position, the yaw angle, the curvature, and the curvature change rate based on one of the right lane marker candidate points and the left lane marker candidate points by the Kalman filter processing.