To provide an apparatus and method for solidifying excavated soil so as to be transported even by a dump truck.

In a line (pressure feed pipe 6) for transferring excavated soil with high moisture content from the excavation spot to a dump truck, a density measuring device (densimeter 5) for measuring the density (sand content) of excavated soil high in water content, a flow rate measuring device (flowmeter 4) for measuring the flow rate of the excavated soil high in water content and a solidifying agent adding device 8 for adding a predetermined amt. of a solidifying agent 11 to the excavated soil high in water content on the basis of the operation value obtained by an operator 10, which operates the addition amt. of the solidifying agent 11 from the density and flow rate obtained from the respective measuring devices, so as to bring the excavated earth and sand high in water content to a state made possible to feed by the dump truck 3.