To reduce the amount of the purged air to be exhausted in a dried air supplying apparatus.

This air dehumidifying apparatus is provided with a plurality of hollow fiber membrane-used dehumidifiers 10, 11. The air dehumidified by a hollow fiber membrane filter 8a of one 10 of the dehumidifiers is supplied to an air-actuated instrument and the outside of its own filter 8a. The purged air passing through the outside of the filter 8a is made to pass through the inside of the other 11 of the dehumidifiers and is dehumidified again. The dehumidified air is reused by being supplied to another instrument 2a being an air supply destination. As a result, the amount of the air to be exhausted is reduced and the air supply efficiency is improved.