PURPOSE: To produce a thin film high in symmetry and uniform in film thickness distribution by specifying the sectional plane shape of a beam on a target of a laser beam.

CONSTITUTION: This thin film is formed by a laser application method in which the target is irradiated with the laser beam in a vacuum chamber and the thin film is grown on a substrate arranged opposite to the target. In this method, the laser beam having cross sectional plane on the target of the laser beam flatter than conversional is emitted. For example, the laser beam having rectangular sectional plane shape on the target of the laser beam and having an aspect ratio of this rectangle of ≤0.2 is used.