Greater emphasis has been placed on smoothness of the floating surface for the applications with floating height of 10 nm or less. To obtain a smooth floating surface, it must be polished with diamond abrasive having a mean particle size of 0.1 μm or less, and conventional ceramic sintered body has poor machinability and it is impossible to use the magnetic heads made of this ceramic sintered body at a floating height of 10 nm or less.The ceramic sintered body according to the present invention contains Al2O3 crystal grains, internal TiC crystal grains existing in the Al2O3 crystal grains and external TiC crystal grains other than the internal TiC crystal grains. The Al2O3 crystal grains and the external TiC crystal grains retain stress caused by the difference in thermal expansion coefficient remaining after sintering, so that the Al2O3 crystal grains and the external TiC crystal grains pull each other in the interface therebetween. As a result, when the ceramic sintered body is machined, micro-cracks generated in the interface can easily grow due to the residual stress in addition to the shearing force caused by the machining operation, so that machinability is improved.