To provide a membrane-type drier for highly dehumidified air capable of supplying stably highly dehumidified air dehumidified highly to a dew point of -50C.

The membrane-type drier 10 has, in a case 14, a housing chamber 14a housing a bundle of hollow-fiber membranes consisting of two or more hollow-fiber membranes 12, a dehumidified air chamber 14c having a dehumidified air discharge outlet 18 which discharges dehumidified air produced by causing moisture absorption air to flow through the hollow-fiber membranes 12 so as to dehumidify and a purge pipe 28 supplying a part of the dehumidified air into the housing chamber as purge air to flow along the outer peripheral surface of the hollow-fiber membranes 12. The hollow-fiber membranes are self-purging ones in which a part of inside air permeates the membrane wall to flow to the outer-periphery side. The purge pipe incorporates a valve 30 adjusting the amount of the purge air so that the dehumidified air discharged from the dehumidified air outlet has a dew point of -50C.