A composite porous object which comprises a biodegradable and bioabsorbable polymer containing bioactive bioceramic particles dispersed therein, the composite porous object having in inner parts thereof large voids 1 having a void diameter of 40-600 .mu.m and small voids 2 having a void diameter of 1 .mu.m or smaller, at least part of the large voids 1 and at least part of the small voids 2 constituting interconnected voids. The small voids 2 are formed in the biodegradable and bioabsorbable polymer walls 3 which surround the large voids 1 and in the surface of the walls 3. It is preferred that 40% or more of all voids constitute interconnected voids. The walls 3 surrounding the large voids 1 in the composite porous object are progressively replaced by bone tissues conducting from the surface of the walls (internal surface of the large voids 1) to inner parts of the walls and by bone tissues conducting from the internal surface of the small voids 2 in the walls 3 toward surrounding parts. The degree of replacement by bone tissues is hence high, and the composite porous object is almost wholly replaced by bone tissues in the living body in a relatively short time period.