To make errors in the exposure of a substrate small, when the pattern of a mask is transferred to the substrate by a scanning exposure system.

While a lit area 21R on a reticle R, having a pattern with an uneven transmissivity distribution in a non-scanning direction (X-direction) is lit with pulse ultraviolet light and an exposed region 21W on the wafer W is exposed to a pattern image in the lit region 21R via a projection optical system PL, scanning exposure is carried out by synchronously moving the reticle R and wafer W in the scanning direction (Y-direction). The transmissivity distribution of the projection optical system P varies gradually and unevenly in the non-scanning direction, because of the unevenness of the transmissivity distribution of the reticle R, so the non-scanning directional transmissivity distribution of light made incident on the exposed region 21W is measured each time a prescribed number of wafers are exposed, and the quantity of exposure of wafers W is controlled by using the transmissivity distribution.