A road surface profile estimating device comprising: an acquisition unit configured to acquire physical quantities representing a motion of a vehicle that is traveling on a road surface; a prediction unit configured to predict, on the basis of a simulation mode including a plurality of parameters, a time evolution of state variables including variables representing an unevenness of the road surface on which the vehicle is traveling and variables representing the physical quantities, wherein simulation model is a half car model for the vehicle; a calculation unit configured to calculate observation values of the physical quantities from the state variables predicted by the prediction unit on the basis of an observation model; an update unit configured to update the state variables through data assimilation between the physical quantities acquired by the acquisition unit and the physical quantities calculated by the calculation unit; an estimation unit configured to estimate respective profiles of the road surface under a first condition and a second condition on the basis of variables representing the unevenness of the road surface, included in the state variables; wherein the profile of the road surface estimated under the first condition is a profile of the road surface estimated on the basis of variables representing a vertical displacement and velocity of a front tire of the half car model, and the profile of the road surface estimated under the second condition is a profile of the road surface estimated on the basis of variables representing a vertical displacement and velocity of a rear tire of the half car model; characterized by a determination unit configured to determine the plurality of parameters such that an absolute value of an evaluation function for evaluating a difference between the profile of the road surface estimated under the first condition and the profile of the road surface estimated under the second condition is equal to or smaller than a threshold value, wherein the evaluation function includes a difference between a first function calculated from the variables representing the vertical displacement and velocity of the front tire and a second function calculated from the variables representing the vertical displacement and velocity of the rear tire. an acquisition unit configured to acquire physical quantities representing a motion of a vehicle that is traveling on a road surface; a prediction unit configured to predict, on the basis of a simulation mode including a plurality of parameters, a time evolution of state variables including variables representing an unevenness of the road surface on which the vehicle is traveling and variables representing the physical quantities, wherein simulation model is a half car model for the vehicle; a calculation unit configured to calculate observation values of the physical quantities from the state variables predicted by the prediction unit on the basis of an observation model; an update unit configured to update the state variables through data assimilation between the physical quantities acquired by the acquisition unit and the physical quantities calculated by the calculation unit; an estimation unit configured to estimate respective profiles of the road surface under a first condition and a second condition on the basis of variables representing the unevenness of the road surface, included in the state variables; wherein the profile of the road surface estimated under the first condition is a profile of the road surface estimated on the basis of variables representing a vertical displacement and velocity of a front tire of the half car model, and the profile of the road surface estimated under the second condition is a profile of the road surface estimated on the basis of variables representing a vertical displacement and velocity of a rear tire of the half car model; characterized by a determination unit configured to determine the plurality of parameters such that an absolute value of an evaluation function for evaluating a difference between the profile of the road surface estimated under the first condition and the profile of the road surface estimated under the second condition is equal to or smaller than a threshold value, wherein the evaluation function includes a difference between a first function calculated from the variables representing the vertical displacement and velocity of the front tire and a second function calculated from the variables representing the vertical displacement and velocity of the rear tire.