A near-field light generating method for irradiating light from a light source to a metal film having a fine opening that has a size of not more than a wavelength of the light emitted from the light source, and forming a fine light spot adjacent to the fine opening on a light outgoing side of the fine opening. The method includes providing the metal film with a rectangular fine opening whose length to width ratio is between 1.1 times and 2 times that of a standard square opening, obtained by increasing the length of the standard square opening, and irradiating the metal film with light from the light source to form the fine light spot, which has a length and a width that are substantially equal to those of the standard square opening, and where the fine light spot has a light intensity, which is not less than two times that of the standard square opening. This method is applicable in a corresponding near-field optical head, which can be included either in an optical microscope to observe a sample surface or in an apparatus for recording and reproducing with respect to a recording medium.
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