Provided is a photocatalyst device that can be implemented using a simple configuration, in which a photocatalyst filter can be cleaned and the performance of the filter restored during maintenance without removal of the filter from the position at which the filter is mounted (while the filter remains mounted). The photocatalyst device comprises a substantially flat plate-shaped photocatalyst filter module (20) including a photocatalyst filter (30) mounted in a substantially vertical direction a cleaning-water supply tube (31) having a slit, the cleaning-water supply tube being secured to the module (20) above the photocatalyst filter (30) and a cleaning-water storage unit (32) having a discharge outlet (21a) and a lid member, the cleaning-water storage unit being provided to the module (20) below the photocatalyst filter (30). When cleaning water (W) is supplied from the exterior to the cleaning-water supply tube (31), the cleaning water (W) flows from the slit along the photocatalyst filter (30) and is temporarily stored in the cleaning-water storage unit (32). When the cleaning water (W) reaches a predetermined amount, the lid member opens, and the cleaning water is discharged from the discharge outlet (21a).Linvention porte sur un dispositif à photocatalyseur pouvant être mis en œuvre à laide dune configuration simple, un filtre à photocatalyseur pouvant être nettoyé et la performance du filtre récupérée pendant lentretien sans enlever le filtre de la position dans laquelle le filtre est monté (alors que le filtre reste monté). Le dispositif à photocatalyseur comprend un module de filtration à photocatalyseur en forme de plaque pratiquement plane (20) comprenant un filtre à photocatalyseur (30) monté pratiquement verticalement un tube dapport deau de nettoyage (31) ayant une fente, le tube dapport deau de nettoyage étant bien fixé au module (20) au-dessus du filtre à photocatalyseur (30) et une unité de stockage deau de nettoyage (32) ayant une sortie dévacuat
