To provide a structurally simple soil improving machine which can prevent the adhesion of sediment with a high water content, highly sticky sediment, etc. and clogging caused by the sediment with a high water content, the highly sticky sediment, etc., and which can perform smooth and efficient treatment.

This traveling soil improving machine (1) is equipped with a hopper (5) for charging the sediment, and a spall carrying-out means (10) which is arranged on the sediment discharge side of the hopper (5); and at least one cutter blade (12) is provided on the sediment slip-down surface of the hopper (5). A clod of the sediment is cut in a proper size with the cutter blade (12) so as to slip down along the sediment slip-down surface. The local adhesion of the sediment and the local clogging caused by the sediment are effectively avoided. A soil improving agent is added to the sediment which is conveyed from the hopper (5) via the means (10); the sediment and the soil improving agent are ground and mixed together so as to be improved to reusable sediment; and the improved sediment is carried out to a prescribed place from a mixer (4) via an improved soil carrying-out means (11).