Fracture toughness by indentation in WC-Co alloys containing addition carbides was determined on the basis of the average distance between the surface crack tips measured on the surface along the directions of Vickers indentation diagonals. Results obtained are as follows. (1) The fracture toughness by indentation agrees well with that obtained by fracture testing. The fracture toughness determination by indentation will be useful because of a simple technique for the rapid evaluation of toughness on small samples.(2) Brittleness parameter, i.e., the hardness fracture toughness ratio which has been proposed for the evaluation of the characteristics of materials, can be applied to cemented carbides. The fracture toughness by indentation and the crack resistance, which are related to the fracture toughness by fracture testing, would be employed instead of the fracture toughness in brittleness parameter.