Disclosed is a flashtube for light irradiation treatment and prevention used for medical treatment or prevention by irradiating a specific part of a living body with light, and the flashtube include a glass valve, and filler gas contained in the glass valve. The filler gas is composed of mixed gas of at least neon gas and xenon gas, and includes the xenon gas in a mixing ratio of 0.23 mol % to 1.21 mol % inclusive relative to 100 mol % of the mixed gas. Thus achieved are the flashtube for light irradiation treatment and prevention and a light irradiation treatment and prevention device capable of producing energy of the light having a wavelength ranging from 600 nm to 700 nm inclusive that are necessary for the light irradiation treatment and prevention without increasing a lighting voltage.
