To provide a mixing equipment for a lightweight granular material into a viscous material for the manufacture of a large amount of a lightweight viscous material by mixing continuously in a short period of time a granular material of small specific gravity into the viscous material such as, for example, dredged earth or a mortar material.

A mixing equipment 10 for storing dredged earth as a viscous material is provided with a pair of extrusion rollers 13a and 13b along and below a discharge opening 12 in a manner of clamping the opening outside a hopper 11 with the opening 12 at its lower end, and a passage 30 for transferring a lightweight granular material on which at least a discharge nozzle section 32 is positioned is set in the hopper 11, and the granular material of small specific gravity is fed continuously onto the passage 30 by a screw feeder 40 as a lightweight granular material feeder and discharged from the discharge nozzle section 32 into the dredged earth and mixed therein.