A method for measuring a synchronization error between a first stage and a second stage in a scanning exposure apparatus including the first stage which supports a reticle, the second stage which supports a substrate, and a projection optical system which projects a pattern of the reticle onto the substrate, the method comprises the steps of measuring, using a measurement unit, a light intensity distribution formed by a measurement pattern while synchronously scanning a measurement mask which has the measurement pattern and is arranged on the first stage, and the measurement unit arranged on the second stage, and calculating the synchronization error between the first stage and the second stage based on a time change in the light intensity distribution measured in the measuring step.