A steering determination device that determines a steering state in which a driver of a vehicle is steering a steering wheel of the vehicle, based on a steering torque of a steering shaft, the device comprising: a torque recognition unit configured to recognize the steering torque based on a result of measurement performed by a torque sensor provided on the steering shaft; an acceleration recognition unit configured to recognize longitudinal acceleration in a longitudinal direction of the vehicle or lateral acceleration in a lateral direction of the vehicle based on a result of measurement performed by an accelerator sensor of the vehicle; a threshold value setting unit configured to set a threshold value used for a determination of the steering state, based on the longitudinal acceleration or the lateral acceleration; and a steering determination unit configured to determine that the driver is in the steering state if the steering torque is equal to or greater than the threshold value, wherein the torque recognition unit is configured to recognize a combined torque of a steering operation torque by the driver's steering operation and a rotation torque by an acceleration acting on the vehicle, as the torque from the steering wheel in the steering torque, and the threshold value setting unit is configured to set the threshold value such that the threshold value decreases as an absolute value of the longitudinal acceleration or the lateral acceleration decreases, in accordance with the rotation torque of the steering wheel generated according to the longitudinal acceleration or the lateral acceleration as the steering torque recognized based on the result of measurement performed by the torque sensor. a torque recognition unit configured to recognize the steering torque based on a result of measurement performed by a torque sensor provided on the steering shaft; an acceleration recognition unit configured to recognize longitudinal acceleration in a longitudinal direction of the vehicle or lateral acceleration in a lateral direction of the vehicle based on a result of measurement performed by an accelerator sensor of the vehicle; a threshold value setting unit configured to set a threshold value used for a determination of the steering state, based on the longitudinal acceleration or the lateral acceleration; and a steering determination unit configured to determine that the driver is in the steering state if the steering torque is equal to or greater than the threshold value, wherein the torque recognition unit is configured to recognize a combined torque of a steering operation torque by the driver's steering operation and a rotation torque by an acceleration acting on the vehicle, as the torque from the steering wheel in the steering torque, and the threshold value setting unit is configured to set the threshold value such that the threshold value decreases as an absolute value of the longitudinal acceleration or the lateral acceleration decreases, in accordance with the rotation torque of the steering wheel generated according to the longitudinal acceleration or the lateral acceleration as the steering torque recognized based on the result of measurement performed by the torque sensor.