To provide a film which, when used as the support layer of a photoresist film for forming a circuit on a base having fine unevenness, indicates excellent base-followability to the fine unevenness, can prevent the generation of defects in the circuit, and is high in transparency and low in film haze.

A biaxially oriented polyester film having trimethylene terephthalate units of at least 80 mole % of the total repeating units is used as the support layer of a photoresist film which has a coefficient of surface orientation (ns) of 0.030-0.115.