A photocatalytic device (1, 1A, 1B, 1C) comprising: a photocatalytic filter (2, 2B) having a surface (2a, 2b) on which a photocatalyst is carried, the photocatalytic filter (2, 2B) being formed of a corrugated member having a plurality of ridges and a plurality of valleys alternately arranged, the photocatalytic filter (2, 2B) having light-passing holes that allow ultraviolet light or visible light to pass therethrough, at top portions of the ridges and bottom portions of the valleys; a light irradiation unit configured to irradiate one of front and rear surfaces of the photocatalytic filter (2, 2B) with ultraviolet light or visible light; a reflection wall facing the other one of the front and rear surfaces of the photocatalytic filter (2, 2B), the reflection wall reflecting light that has been emitted from the light irradiation unit and has passed through the light-passing holes of the ridges and the valleys of the photocatalytic filter (2, 2B), toward the other surface; a gas inflow part and a gas outflow part respectively provided at one end and the other end of the photocatalytic filter (2, 2B), the gas inflow part and the gas outflow part allowing a gas to flow in a space between the light irradiation unit and the photocatalytic filter (2, 2B) and a space between the reflection wall and the photocatalytic filter (2, 2B), over the front and rear surfaces of the photocatalytic filter (2, 2B) from the one end toward the other end along a direction in which the ridges and the valleys extend; and a support member (5, 5A, 5B, 501, 502) configured to support the photocatalytic filter (2, 2B) at the one end or the other end, wherein the support member (5, 5A, 5B, 501, 502) supports the light irradiation unit; and characterized in that the support member (5, 5A, 5B, 501, 502) is metallic and the photocatalytic filter (2, 2B) is metallic, the corrugated member being made of a metal material. a photocatalytic filter (2, 2B) having a surface (2a, 2b) on which a photocatalyst is carried, the photocatalytic filter (2, 2B) being formed of a corrugated member having a plurality of ridges and a plurality of valleys alternately arranged, the photocatalytic filter (2, 2B) having light-passing holes that allow ultraviolet light or visible light to pass therethrough, at top portions of the ridges and bottom portions of the valleys; a light irradiation unit configured to irradiate one of front and rear surfaces of the photocatalytic filter (2, 2B) with ultraviolet light or visible light; a reflection wall facing the other one of the front and rear surfaces of the photocatalytic filter (2, 2B), the reflection wall reflecting light that has been emitted from the light irradiation unit and has passed through the light-passing holes of the ridges and the valleys of the photocatalytic filter (2, 2B), toward the other surface; a gas inflow part and a gas outflow part respectively provided at one end and the other end of the photocatalytic filter (2, 2B), the gas inflow part and the gas outflow part allowing a gas to flow in a space between the light irradiation unit and the photocatalytic filter (2, 2B) and a space between the reflection wall and the photocatalytic filter (2, 2B), over the front and rear surfaces of the photocatalytic filter (2, 2B) from the one end toward the other end along a direction in which the ridges and the valleys extend; and a support member (5, 5A, 5B, 501, 502) configured to support the photocatalytic filter (2, 2B) at the one end or the other end, wherein the support member (5, 5A, 5B, 501, 502) supports the light irradiation unit; and characterized in that the support member (5, 5A, 5B, 501, 502) is metallic and the photocatalytic filter (2, 2B) is metallic, the corrugated member being made of a metal material.