The effect of surface modified Si-Al-C® fibre with carbon interface (SA/C fibre) addition on the densification of silicon carbide (SiC) composite was examined. An acid treatment (H2SO4 and HNO3) was carried out at 50°C for 3 h in order to add COO- group to the surface of SA/C fibre and to enhance the dispersibility of SA/C fibre in the SiC powder due to the mixing operation in the polar solvent. Commercially available ultrafine SiC powder (specific surface area: 47.5 m2∙g-1) was mixed with acid-treated SA/C fibre and sintering aid (4.8 mass% Al4C3 and 1.2 mass% B4C) in the presence of acetone. The relative density of the SiC composite with non-acid-treated SA/C fibre addition hot-pressed at 1800°C for 1 h in Ar atmosphere under a pressure of 62 MPa was 98.4%, whereas that of the SiC composite with acid-treated SA/C fibre addition increased to 98.7%. Furthermore, the fracture toughness increased from 5.6 MPa∙m1/2 to 7.0 MPa∙m1/2 for the acid-treated SA/C fibre addition.