PROBLEM TO BE SOLVED: To provide a phototherapy device and a phototherapy method capable of obtaining an excellent skin treatment effect while suppressing immediate blackening. A light treatment device (10) includes a light source unit that irradiates an affected area with treatment light. The light source unit has a peak wavelength within a wavelength range of 365 ± 5 nm, and emits light including a plurality of LED elements that emit light including light having a wavelength of 350 nm or less and emitted light of the plurality of LED elements to emit therapeutic light. A light irradiation window and a filter that substantially blocks light having a wavelength of 350 nm or less among the light emitted from the plurality of LED elements are provided. [Selection diagram]【課題】即時黒化を抑制しつつ、優れた皮膚治療効果を得ることができる光線治療装置および光線治療方法を提供する。【解決手段】光線治療装置１０は、患部に治療光を照射する光源部を備える。光源部は、波長３６５±５ｎｍの範囲にピーク波長を有し、波長３５０ｎｍ以下の光を含む光を放射する複数のＬＥＤ素子と、複数のＬＥＤ素子の放射光が入射されて治療光を放出する光照射窓と、複数のＬＥＤ素子の放射光のうち、波長３５０ｎｍ以下の光を実質的に遮断するフィルタと、を備える。【選択図】 図１
