Provided is a small and handy phototherapy apparatus that receives an ultraviolet light source in a housing, and is able to appropriately irradiate a patient with ultraviolet light emitted from the ultraviolet light source while not irradiating an operator with the ultraviolet light. The phototherapy apparatus is characterized in that the housing has a light guide path through which the ultraviolet light from the ultraviolet light source passes, a leading end of the light guide path has an irradiation window for emitting the ultraviolet light to the outside, and an observation window or windows are formed in at least one side surface of the light guide path near the irradiation window, whereby irradiation treatment while observing an affected part becomes possible, and irradiation of only the affected part with the ultraviolet light becomes possible without erroneously irradiating other parts with the ultraviolet light.
