A laser spray method exhibiting a high detection sensitivity when applied to mass analysis has its sensitivity raised further. In a laser spray method of ionizing a liquid sample by irradiating, with a laser beam, the end of a capillary into which the sample has been introduced, use is made of an infrared laser as the laser beam, at least the end of the capillary is formed of a substance that does not readily absorb the laser beam used, and either the capillary is formed of a conductor and a high voltage is applied thereto, or the capillary is formed of an insulator, a conductive wire is placed inside a small cavity of the capillary and a high voltage is applied to the conductive wire.