A rider characteristic determining method for determining control characteristics of a rider controlling a saddle riding type vehicle, comprising: detecting at least one of a yaw rate and a yaw angle of the saddle riding type vehicle by a first vehicle state detector; a turning movement discriminating step that discriminates a section where the saddle riding type vehicle has made a turning movement; detecting at least one of a roll rate, a roll angle, a pitch rate, a pitch angle, and a caster angle of the saddle riding type vehicle by a second vehicle state detector; a component separating step that separates detection values detected by the first vehicle state detector and the second vehicle state detector in the turning movement section discriminated by the turning movement discriminating step, into adjustment components that are high-frequency band components higher than a threshold frequency set beforehand, and prediction components that are low-frequency band components lower than the threshold frequency; a turning characteristic determining step that determines a turning characteristic of the saddle riding type vehicle, wherein the turning characteristic determining step includes a turning performance score calculating step that calculates a turning performance score of the saddle riding type vehicle based on the prediction components separated from the detection value of the second vehicle state detector by the component separating step, and the method further comprises a vehicle stability characteristic determining step that determines a vehicle stability characteristic of the saddle riding type vehicle, wherein the vehicle stability characteristic determining step includes a vehicle stability score calculating unit that calculates a vehicle stability score of the saddle riding type vehicle based on a ratio between the adjustment components and the prediction components separated from the detection value of the first vehicle state detector by the component separating unit. detecting at least one of a yaw rate and a yaw angle of the saddle riding type vehicle by a first vehicle state detector; a turning movement discriminating step that discriminates a section where the saddle riding type vehicle has made a turning movement; detecting at least one of a roll rate, a roll angle, a pitch rate, a pitch angle, and a caster angle of the saddle riding type vehicle by a second vehicle state detector; a component separating step that separates detection values detected by the first vehicle state detector and the second vehicle state detector in the turning movement section discriminated by the turning movement discriminating step, into adjustment components that are high-frequency band components higher than a threshold frequency set beforehand, and prediction components that are low-frequency band components lower than the threshold frequency; a turning characteristic determining step that determines a turning characteristic of the saddle riding type vehicle, wherein the turning characteristic determining step includes a turning performance score calculating step that calculates a turning performance score of the saddle riding type vehicle based on the prediction components separated from the detection value of the second vehicle state detector by the component separating step, and the method further comprises a vehicle stability characteristic determining step that determines a vehicle stability characteristic of the saddle riding type vehicle, wherein the vehicle stability characteristic determining step includes a vehicle stability score calculating unit that calculates a vehicle stability score of the saddle riding type vehicle based on a ratio between the adjustment components and the prediction components separated from the detection value of the first vehicle state detector by the component separating unit.