A rotation angle detection device comprising: a detection portion adapted to detect a detection angle (θ) that univocally corresponds to a rotation angle (θr) of a rotating body within a predetermined range, that is a limited range the rotating body is able to rotate, wherein the detection angle (θ) linearly increases from a minimum value (θmin) to a maximum value (θmax) as the rotation angle (θr) increases within a unit range, that is a range the detection portion is able to detect a detection angle (θ) linearly without correcting the detection angle (θ), so that a characteristic curve showing a relation between the rotation angle (θr) and the detection angle (θ) has linear characteristics if the predetermined range, for which the width of range is narrower than the width of the unit range, is contained in the unit range, and the detection angle (θ) changes from the maximum value (θmax) to the minimum value (θmin) or from the minimum value (θmin) to the maximum value (θmax) at the boundary between unit ranges that are adjacent to each other; and a correction portion adapted to correct the detection angle (θ) so that the characteristic curve showing the relation between the rotation angle (θr) and the detection angle (θ) has linear characteristics over the entire predetermined range; characterized in that the correction portion is adapted to correct the detection angle (θ) by respectively adding or subtracting a value (θall) obtained by subtracting the minimum value (θmin) from the maximum value (θmax) when the detection angle (θ) changes from the maximum value (θmax) to the minimum value (θmin) or from the minimum value (θmin) to the maximum value (θmax) at the boundary between the unit ranges which is contained in the predetermined range. a detection portion adapted to detect a detection angle (θ) that univocally corresponds to a rotation angle (θr) of a rotating body within a predetermined range, that is a limited range the rotating body is able to rotate, wherein the detection angle (θ) linearly increases from a minimum value (θmin) to a maximum value (θmax) as the rotation angle (θr) increases within a unit range, that is a range the detection portion is able to detect a detection angle (θ) linearly without correcting the detection angle (θ), so that a characteristic curve showing a relation between the rotation angle (θr) and the detection angle (θ) has linear characteristics if the predetermined range, for which the width of range is narrower than the width of the unit range, is contained in the unit range, and the detection angle (θ) changes from the maximum value (θmax) to the minimum value (θmin) or from the minimum value (θmin) to the maximum value (θmax) at the boundary between unit ranges that are adjacent to each other; and a correction portion adapted to correct the detection angle (θ) so that the characteristic curve showing the relation between the rotation angle (θr) and the detection angle (θ) has linear characteristics over the entire predetermined range; characterized in that the correction portion is adapted to correct the detection angle (θ) by respectively adding or subtracting a value (θall) obtained by subtracting the minimum value (θmin) from the maximum value (θmax) when the detection angle (θ) changes from the maximum value (θmax) to the minimum value (θmin) or from the minimum value (θmin) to the maximum value (θmax) at the boundary between the unit ranges which is contained in the predetermined range.