The liquid-phase concentration from the interior to the surface region and its influence on the microstructural changes were investigated in pressureless sintered $eta$-SiC Surface reaction-layer was formed by reaction of packing powder and volatile components on the surface during sintering which was induced the concentration of liquid-phase in the surface regions. The microstructural changes between the surface region and the interior were appeared in sintered specimen which was resulted from the difference of liquid-phase content during sintering. Microstructural changes were observd with the depth of about 250${mu}{ extrm}{m}$ from he surface. The grain size and aspect ratio of SiC in the interior are larger than those in the surface region and the rate of transforma-tion of $eta$-to $alpha$-SiC during sintering is higher in the interior than that in the surface region.