1. An exposure apparatus inspection method, comprising providing illumination light obliquely incident on a mask from a direction tilted with respect to an optical axis of an illumination optical system, projecting light diffracted at the mask onto an image receptor via a projection lens, and transferring a pattern formed on the mask onto the image receptor, the pattern formed on the mask including a first pattern formed as a periodic pattern, a second pattern formed as a periodic pattern having a period larger than a period of the first pattern in the same direction as the period of the first pattern, a third pattern formed as a periodic pattern in a periodic direction different from a periodic direction of the first and second patterns, and a fourth pattern formed as a periodic pattern having a period larger than a period of the third pattern in the same direction as the period of the third pattern, the illumination light being obliquely incident on the first pattern and the second pattern from a first oblique direction, the illumination light being obliquely incident on the third pattern and the fourth pattern from a second oblique direction different from the first oblique direction, a relative distance from a transfer pattern of the first pattern to a transfer pattern of the second pattern transferred onto the image receptor and a relative distance from a transfer pattern of the third pattern to a transfer pattern of the fourth pattern transferred onto the image receptor being measured, and an optical characteristic of the exposure apparatus being ascertained based on the two relative distances.