A plastic sintered body has a first compressed portion formed by heating plastic powder packed in a cavity of a metal mold and sintering a first portion of the plastic powder packed in the cavity in a first compression state. In addition, a second compressed portion is formed by sintering a second portion of the plastic powder packed in the cavity in a second compression state. A plurality of interconnected minute voids are formed in the first compressed portion and a plurality of interconnected minute voids smaller than the voids in the first compressed portion are formed in the second compressed portion. The manufacturing of the plastic sintered body as noted above is performed continuously in the metal mold. In addition, two types of porous portions including voids of different sizes are formed by sintering only one type of the plastic powder in the metal mold.