An image projection device includes: a light source for emitting a light beam; a mirror unit that includes a mirror for reflecting the beam and projects an image onto a surface by rotating the mirror about a rotational axis to scan the beam; and a controller for determining, according to a function representing a relationship between a shift amount, an emitting time of the beam, a position on the surface irradiated by the beam emitted at the emitting time, and a shift angle of the mirror from its position when it is not driven, the emitting time corresponding to a target position. The shift amount is a shift amount of a position of the beam incident on the mirror or a shift amount of a position of the source relative to an optical axis of light incident on the mirror without the shift amount and perpendicularly intersecting the rotational axis.