A steering assist device, comprising: an electric motor that applies a steering driving force to a steering operation mechanism of a vehicle; an information obtaining unit that obtains a lateral deviation of the vehicle from a target travel line, a lateral deviation change rate or a rate of change in the lateral deviation per unit time, and a rate of change in the lateral deviation change rate per unit time; a steering assist current value setting unit that sets a steering assist current value corresponding to a target value of steering assist torque; a lane keep assist current value calculation unit that calculates a lane keep assist current value that makes the lateral deviation and the lateral deviation change rate closer to zero, based on the lateral deviation and the lateral deviation change rate obtained by the information obtaining unit; a correction unit that corrects the lane keep assist current value calculated by the lane keep assist current value calculation unit so that an absolute value of the lane keep assist current value increases, if the lateral deviation change rate and the rate of change in the lateral deviation change rate per unit time obtained by the information obtaining unit have the same sign; a target current value calculation unit that calculates a target current value by using the steering assist current value set by the steering assist current value setting unit and the lane keep assist current value corrected by the correction unit; and a control unit that drivingly controls the electric motor based on the target current value calculated by the target current value calculation unit. an electric motor that applies a steering driving force to a steering operation mechanism of a vehicle; an information obtaining unit that obtains a lateral deviation of the vehicle from a target travel line, a lateral deviation change rate or a rate of change in the lateral deviation per unit time, and a rate of change in the lateral deviation change rate per unit time; a steering assist current value setting unit that sets a steering assist current value corresponding to a target value of steering assist torque; a lane keep assist current value calculation unit that calculates a lane keep assist current value that makes the lateral deviation and the lateral deviation change rate closer to zero, based on the lateral deviation and the lateral deviation change rate obtained by the information obtaining unit; a correction unit that corrects the lane keep assist current value calculated by the lane keep assist current value calculation unit so that an absolute value of the lane keep assist current value increases, if the lateral deviation change rate and the rate of change in the lateral deviation change rate per unit time obtained by the information obtaining unit have the same sign; a target current value calculation unit that calculates a target current value by using the steering assist current value set by the steering assist current value setting unit and the lane keep assist current value corrected by the correction unit; and a control unit that drivingly controls the electric motor based on the target current value calculated by the target current value calculation unit.