To provide a method for washing a pipe transfer system and a device therefor which have simple construction and are inexpensive and simple to handle and sanitary, and are suitable particularly for granular substances of raw material of food, or the like.

In this device, each cyclone upper cover and covers provided with air bleeder pipes 24, 34 and overflow pipes 25, 35 can be freely changed. A cover in which a connecting pipe 14 to a holding tank 9 from the lower part of a cyclone 3 is provided with an air blowing port 38 is made as a washing cover 39. The upper region of a connecting pipe 16 to the upper part of a cyclone 10 from the upper end of the holding tank 9 is provided with an air bleeder 37 and the lower end of the holding tank 9 is provided with a changeover for drainage. A washing outlet cover 29 provided with an air blowing port 27 and a drainage port 28 is applied to a region from which the connection to the cyclone 3 and equipments is removed. To the feeding port end part of material to be treated, a washing pipe 33 provided with a warm water or steam injection pipe 30 and a switching pipe drain cover 31 for drainage and a hot air connecting pipe 32 is attached.