A purpose of the present invention is to provide a photocatalytic device that can not increase a flow resistance of gas, can obtain the miniaturization of thickness and diameter of a device, has a simple structure, can realize energy-saving and low cost, and also can solve a thermal problem. The photocatalytic device of the solving means is equipped with: a photocatalytic filter (2) consisting of a wave-shaped member (20), wherein light-passing holes (23) allowing ultraviolet ray or visible light to pass are respectively formed at top portions of mountain portions (21) and bottom portions of valley portions (22), and a photocatalyst is supported on a surface thereof； a light irradiating portion (3) irradiating a face (2a) of one side of the surface inner faces of the photocatalytic filter (2) with the ultraviolet ray or the visible light； a reflecting wall (4) disposed at one side opposite to a face (2b) of another side of the photocatalytic filter (2) to allow the light that is emitted from the light irradiating portion (3) and goes through the light-passing holes (23) of the photocatalytic filter (2) to be reflected toward the face (2b) of the another side thereof； and an inflow portion (11) and an outflow portion (12) of gas respectively allowing gas to flow between a space (s1) between the light irradiating portion (3) and the photocatalytic filter (2) and a space (s2) between the photocatalytic filter (2) and the reflecting wall (4), from one end side toward another end side along an extending direction of the mountain portion and the valley portion on the surface/inner faces of the photocatalytic filter (2).本發明的課題為提供一種光觸媒裝置，不會增加氣體的流通阻力，並可獲得裝置之薄型化與細徑化等的小型化，且構造也簡易，可實現節能、低成本化，也可解決熱的問題。其解決手段之光觸媒裝置，具備：光觸媒濾器(2)，係由波形的構件(20)所構成，在山部(21)的頂部及谷部(22)的底部分別形成有紫外線或可視光的光通過的光通過孔(23)，在表面支承有光觸媒；光照射部(3)，係對此光觸媒濾器(2)之表內面的其中一方的面(2a)照射紫外線或可視光的光；反射壁(4)，係設置在與光觸媒濾器(2)的另一方的面(2b)對面的一側，使得從光照射部(3)照射通過光觸媒濾器(2)的光通過孔(23)的光朝向另一方的面(2b)反射；及氣體的流入部(11)及流出部(12)，分別使氣體在光觸媒濾器(2)的表/內面上沿著山部及谷部延伸的方向從一端側朝另一
