Synopsis: It is well known that the columnar dendrite grows in a direction opposing the liquid flow. Therefore, in order to make clear the fluid flow within liquid pool, the solidification structures of steel slabs cast continuously by the curved mould bending type machine were investigated. At the same time, the amount of large inclusions trapped within the upper part of slab was measured by the method of X-ray radiography. The following results were obtained; (1) The deflection angle of columnar dendrite, depending on the solidification rate and the flow velocity along the solidified shell, is large at the edge of slab, but smaller near to the center of slab. (2) The amount of large inclusions in the accumulated zone of slab increases in proportion to its deflection angle of columnar dendrite. (3) In case of the asymmetrical flow from nozzle pores, the distribution of large inclusions in the direction of slab width becomes asymmetrical, and the amount of large inclusions extremely increases at the edge of strong flow side.