To pour many granular materials into a fluid conveying channel in a separately sealed state and to efficiently convey them, sequentially.

A granular material send-in device 4 is attached to a high pressure fluid conveying channel 1, fluid inside the channel is sealed, and the granular materials 18 are stored in many storage holes 6 provided continuously on the upper surface of a conveying belt 5. Then, by moving the conveying belt 5 into the channel while sealing them, the granular materials 18 inside the storage holes 6 are sent out to flow inside the channel 1, sequentially.