The fracture toughness of a crystalline silicon carbide fiber, Tyranno-SA((R)), was determined by introducing an artificial notch directly into the fiber test specimens using a focused-ion (Ga+) beam. The relation between fracture strength and notch size was determined experimentally, while the relation among the notch size, fiber diameter, applied stress at infinity, and stress intensity factor was analyzed by the finite element method. By applying the analyzed result to the experimental results, the fracture toughness of the fiber was determined to be 2.7 +/- 0.4 MPa root m.