To provide a mobile type silo and a plant system to flexibly comply with the change of kinds of powder even when various kinds of ready-mixed concrete are manufactured and to be realized at a low cost through comparatively simple constitution.

A-plant system is provided with a tank 3 to store a given amount of powder, a root blower 8 to effect pneumatic transportation of powder flowing out from the under side of the tank 3, and a rotary feeder 9. A mobile type silo 2 the whole of which is movable is coupled to a plant 20, comprising a hopper 21 to receive powder; a metering apparatus 23 to meter powder; and a mixer 25 to mix together powder, aggregate, and water, through a transport pipe 11. The powder pneumatically transported by the root blower 8 and the rotary feeder 9 is conveyed in the hopper 21 through the transport pipe 11 and after metering by the metering apparatus 23, the powder flows in the mixer 25.