The abnormality determination apparatus, which is for determining presence of an abnormality in an angle detection device configured to output an output signal having a value equivalent to a rotational angle of a rotating body, includes a smoothing device configured to receive the output signal of the angle detection device to smooth a dependent variable of a function whose independent variable is the rotational angle equivalent value, and a parameter calculation device for calculating an abnormality determination parameter based on the dependent variable smoothed by the smoothing device. The function is such that an integrated value of the rotational angle equivalent value over a predetermined time section is always positive or negative, and is configured to vary the dependent variable continuously in accordance with continuous variation of the independent variable in at least a part of the predetermined time section.