PURPOSE: To efficiently mold a homogeneous molded article by heating a powdery ultra-high mol.wt. polyethylene polymer at a specified temp. without applying pressure in a mold loosely clamped by a male mold and cooling it to room temp. under a specified pressure.

CONSTITUTION: A powdery ultra-high mol.wt. polyethylene polymer is filled in a mold being loosely clamped by a male mold. Under this condition, the powder is heated at 220-250°C in the male mold at a low pressure of up to 0.5 MPa or without applying pressure. This heating is made in such a way that heat is fed from press faces of the top mold and the bottom mold of a press to make temp. of the whole part of the powdery sediment in the above described temp. range. When the temp. reaches the above described temp., the polymer in the mold is immediately placed at a pressure of 8-14 MPa and is cooled to room temp. while this pressure is held. It is possible thereby to prepare a homogeneous molded article with a specified measure and to make efficiency of press molding high.