To make net shape forming possible, in particular to improve a yield of a thin sintered body and to reduce the production cost by efficiently conducting capsule removal after hot isostatic pressing(HIP) when producing of a porous sintered body, which is subjected to HIP with filling a metal powder in a metal capsule.

Metal capsule removal after HIP treatment is conducted by chemical dissolving (a dissolving solution can dissolve the capsule but does not have dissolving capability for a product sintered body). When the capsule is changed to a non-dissolvable composition by diffusion reaction of a boundary between the capsule and a metal powder, a ceramic powder layer of non-binding as a barrier layer is interposed. The ceramic powder layer is fallen off from a sinterd body surface by capsule dissolving treatment after HIP.