In the present invention, a photocatalytic device is formed by providing a gas inflow part and a gas outflow part for a gas at both end positions of a photocatalytic filter instead of providing a gas inlet-side flow channel and a gas outlet-side flow channel at positions facing the filter surface, while maintaining the contact area between the gas and the filter surface by adopting a waveform member as the photocatalytic filter and causing the gas to flow in the direction in which the ridges and valleys extend, over the front and rear surfaces of the filter from one end to the other end. Accordingly, there is no increase in flow resistance of the gas, the device can be made smaller by thinning the device, reducing the diameter, or the like, light irradiation efficiency can be improved, energy consumption and costs can be reduced, and the problem of heat can be resolved with a simple structure.
