A photomask for focus monitoring of the present invention is provided with a substrate that allows the exposure light to pass through and a unit mask structure for focus monitoring. Unit mask structure for focus monitoring has two patterns, and that are formed on the surface of substrate and a light blocking film that has a rear surface pattern that is formed on the rear surface of substrate for substantially differentiating the incident directions of the exposure light that enters two patterns, and for position measurement. When the dimension of rear surface pattern is L and the wavelength of the exposure light is &lgr;, L/&lgr; is 10, or greater.