An adjustment method for adjusting the direction of infrared light projected so that infrared light to pass over a displayed image from a projection device that is rotatable with orthogonal first and second axes as axes of rotation, the method including: arranging the projection device such that the plane containing the first axis and a line perpendicular to the upper edge or lower edge of the displayed image is orthogonal to the plane in which the displayed image is displayed; displaying a first image representing a first target on the line; and rotating the projection device with the second axis as the axis of rotation such that the irradiation position of the infrared light upon an indicator in the first image, in which is displayed a captured image, coincides with the position of the first target on the first image.