We manufactured ultrafine grain cemented carbides with the WC grain size up to 0.4μm and measured their properties. Ultrafine grain cemented carbides have higher hardness and strength and equivalent or higher toughness than conventional cemented carbides, and their thermal expansion and elastic modulus are close equivalent to steel materials. Thus, ultrafine grain cemented carbides are available for cutters, knives and other wear-resistant parts. It is confirmed that the finer grain size and defects become, the more the properties are improved.