A ceramic sintered body containing aluminum oxide, tungsten carbide and zirconium oxide, wherein: the zirconium oxide contains ZrO and ZrO2; the ZrO2 has a crystal structure or structures of one or two kinds selected from the group consisting of a tetragonal crystal structure and a cubic crystal structure; and when, in X-ray diffraction, regarding a peak intensity for a (111) plane of the ZrO as being denoted by I1, regarding a peak intensity for a (101) plane of ZrO2 having a tetragonal crystal structure as being denoted by I2t, and also regarding a peak intensity for a (111) plane of ZrO2 having a cubic crystal structure as being denoted by I2c, a ratio of I1 based on a total of I1, I2t and I2c [I1/(I1+I2t+I2c)] is from 0.05 or more to 0.90 or less.