To provide a high-precision size controlling method in the manufacturing of photomask.

The method for manufacturing photomask comprising forming a resist pattern and patterning the light-shielding layer by dry etching using the resist pattern as a mask, includes, after forming a resist pattern, a first control step ST-6 and a second control step ST-7. The ST-6 comprises measuring the size of the resist pattern (ST6-1), predicting the size of a light-shielding pattern from the result of the ST6-1 (ST6-2), and correcting a deviation from a finished measurement by changing at least one of the two process conditions, descum (ST6-3) and dry-etching (ST6-4). The ST-7 comprises measuring the size of a light-shielding pattern with resist after dry etching and before removing the resist (ST7-1), predicting the size of the light-shielding pattern from the result of the ST7-1 (ST7-2), and correcting a deviation from a finished dimension by additional dry-etching (ST7-3).