The present invention provides a technique of improving wear resistance of a Sialon sintered body. The Sialon sintered body has a Sialon phase including at least a β-Sialon and a 12H-Sialon among an α-Sialon, the β-Sialon and the 12H-Sialon. A ratio of a second Sialon total content, which is a sum of the contents of the α-Sialon and the 12H-Sialon, to a first Sialon total content, which is a sum of contents of the α-Sialon, the β-Sialon and the 12H-Sialon, is greater than 20% and not greater than 55%, and a ratio of the content of the 12H-Sialon to the first Sialon total content is not less than 2% and not greater than 55%.