A dense ceramic sintered body is appropriately manufactured. A manufacturing method for the ceramic sintered body includes: a step of performing heat treatment on a ceramic green body as a green body of ceramic powder under a first condition; a step of performing heat treatment, under a second condition with a higher pressure than the first condition, on the ceramic green body subjected to the heat treatment under the first condition; and a step of performing heat treatment, under a third condition with a higher pressure than the second condition, on the ceramic green body subjected to the heat treatment under the second condition to manufacture the ceramic sintered body.