It is intended to provide an apparatus for dilating the vascular wall with the use of a high-intensity pulsed light. A vasodilator with the use of high-intensity pulsed light irradiation comprising a high-intensity pulsed light irradiation system, which is a high-intensity pulsed light irradiation system capable of generating steam bubbles in a vessel and having a high-intensity pulsed light generation unit, a high-intensity pulsed light transfer unit and a unit of irradiating the high-intensity pulsed light in a vessel, whereby steam bubbles are generated in the vessel by the irradiation with the high-intensity pulsed light and thus the vascular wall is spread and the vessel is dilated due to the function of the vapor bubbles.
