A ring shear apparatus for measuring a shear strength of soil samples. The ring shear apparatus considering a wall-slip effect including: an upper ring for forming a first accommodation portion having a ring shape in which soil samples are accommodated; a lower ring for forming a second accommodation portion that corresponds to the first accommodation portion of the upper ring and has a ring shape in which soil samples are accommodated, closely attached to a lower portion of the upper ring and rotatably installed relative to the upper ring; a rotating unit for rotating the lower ring relative to the upper ring; and a shear strength measuring sensor combined with the upper ring and for measuring a shear strength of the soil samples, wherein a plurality of protrusions that protrudes from the lower ring is formed on an inner circumferential surface of the lower ring along a circumferential direction of the lower ring in order to prevent the soil samples from being slid when the lower ring is rotated.