the through hole 365 passes through both a central portion of the filter part 351 and an outer portion of the filter part through the stepped grooves 371 and 373 along the inclined portions 371 c and 373 c that is air uniformly passes through the entire surface of the filter part so that durability and filtering efficiency of the filter part can be considerably improved the body part 360 is divided into upper and lower portions 361 and 363 from the through hole 365 the upper and lower portions 361 and 363 of the body part 360 are provided with storage parts 380 containing the ingredient of phytoncide the storage part 380 has a storage recess 381 with upper or lower side opened and a cover 383 which opens or closes the storage recess 381 the storage recess 381 is defined from the through hole 365 by a partition wall so the ingredient of phytoncide contained in the storage recess does not directly contact air passing through the through hole 365 and thus can be used for a long term the cover 383 has protrusions 385 at opposite sides and the storage recess 381 has grooves 387 into which the protrusions 385 are fitted the storage recess 381 has stopper portions 382 a and 382 b at inner sides thereof the stopper portions 382 a and 382 b serve to restrict a maximum distance at which the cover 383 is lowered thereby preventing the cover 383 from being.