A color wheel driving motor includes a magnet arranged radially outward of a rotor holder. The ring-shaped magnet includes n number of N-pole and n number of S-pole and magnetic pole changeover portions arranged between the poles. The magnetic pole changeover portions are arranged at an angular interval of 360°/2n, the n being a positive integer. On an imaginary plane perpendicular to the center axis, a first straight line passing through the center axis and at least one of the 2n magnetic pole changeover portions makes a specified angle &thetas; with respect to a second straight line extending from the center axis toward the ring-shaped magnet. A first mark is arranged in a region of a surface of the ring-shaped magnet where the second straight line overlaps with the ring-shaped magnet, the specified angle &thetas; being equal to or larger than 0° and equal to or smaller than 360°/2n.
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