A film-forming method is provided for forming a planar periodic structure having a predetermined periodicity by depositing liquid material on an object. A liquid drop supplying means is used which supplies a liquid drop at a predetermined driving period to deposit the liquid material on the object; the presence or absence of the supply of the liquid drop is controlled at each driving period in accordance with the periodicity of the planar periodic structure to be formed; and the liquid drop is supplied by controlling the liquid drop supplying means while the liquid drop supplying means is scanned at a predetermined scanning speed in a predetermined scanning direction relative to the object. A natural number times a value obtained by multiplying the driving period and the scanning speed is set to be the structural period of the planar periodic structure in the scanning direction.