To provide a mammary prosthesis for facilitating an adjustment of installation weight and dehydration-drying in bathing or water washing, by imparting it with an appearance, touch, a color, flexibility and sweat absorptivity of a human body mamma.

A mamma inner layer 30 sealed by respective thin films 21 and 22, is formed by forming a mamma surface layer 10 made of a fine continuous porous synthetic resin or rubber and a mamma bottom surface layer 40 made of the fine continuous porous synthetic resin or rubber; applying the synthetic resin or rubber thin film 21 to a reverse surface of the mamma surface layer 10; and applying the synthetic resin or rubber thin film 22 to a reverse surface of the mamma bottom surface layer 40.