An ultraviolet irradiation device includes: a lamp house having at least one surface formed with a light extraction surface; an excimer lamp that is accommodated in the lamp house at a position apart from the light extraction surface in a first direction, the excimer lamp emitting ultraviolet light having a main emission wavelength belonging to a first wavelength band of 190 nm or more and 225 nm or less; a pair of electrodes that applies a voltage to a light-emitting tube of the excimer lamp; an optical filter that is disposed on the light extraction surface, and that substantially transmits the ultraviolet light having the first wavelength band and substantially fails to transmit ultraviolet light having a wavelength of 240 nm or more and 300 nm or less; and a light diffuser that is disposed between the excimer lamp and the optical filter in the lamp house in the first direction, for diffusing and reflecting light incident on the light diffuser.