To provide a mud treatment device capable of producing a uniform lump of mud even for mud with high viscosity.

The mud treatment device 11 includes a mud receiving tank 12 storing mud 5, a slurry tank 23 stirring the mud 5 sent out from the slurry tank 23 and a high pressure filter press 30 dehydrating the mud 5 sent out from the slurry tank 23. A circulating pump 28 vertically circulating the mud 5 in the slurry tank 23 is provided to the slurry tank 23. Since particles with large diameters and precipitated downward are thereby again carried to the upper part to enable the mud 5 to forcedly and vertically circulate, slurry liquid having uniform viscosity distribution can be produced without storing the particles with large diameters in the lower part of the slurry tank 23, and as a result, the lump of mud dehydrated and formed by the high pressure filter press can be also formed of the uniform viscosity distribution and the uniform degree of dehydration.