Provided are a photomask, a method for manufacturing the photomask and a method for measuring optical characteristics of a wafer exposure system, the measuring method using the photomask during manufacture. The photomask includes a substrate and a measuring pattern including a light opaque region pattern formed on the substrate and a plurality of light transmitting region patterns that are formed in regions divided by the light opaque region pattern and provoke phase shifts to provide phase differences to light transmitted through light transmitting regions. Precise measurements of the degree of a focus and lens aberrations of an exposure system using the photomask are obtained.