PURPOSE: To shorten an open-close stroke of a press apparatus compressing simultaneously mats piled in multiple stages when a wooden cement sheet is prepd.

CONSTITUTION: An upper platen 10 is placed on multiple mats 3 piled on a lower platen 6 by means of an upper side platen elevating apparatus and the mats 3 of each stage is preliminarily compressed by the dead wt. of the upper platen 10 to decrease the piling height of the mats 3. The mats 3 of multiple stages with a decreased piling height are compressed by means of a press apparatus 12 to connect the upper platen 10 and the lower platen 6 and to keep the mat 3 of each stage under a compressed condition. The mats 3 of multiple stages kept under the compressed condition are cured and then, they are compressed by means of the press apparatus 12 to disconnect the upper platen 10 with the lower platen 6. The upper platen 10 is removed from the cured mats 3 of multiple stages by means of the upper side platen elevating apparatus 8.