PURPOSE: To produce a uniform honeycomb-like rib and lighten the product by a method wherein hexagonal inserts are provided on the forming surface, which corresponds to the rear surface of the product, of a mold and a gap is provided at each joining part of the insert and the mold in order to exhaust air naturally.

CONSTITUTION: Hexagonal prismatic projections 16, 16a... or inserts 13, 13a... are provided on the forming surfaces 3 and 4 of molds 2 and 2a so as to have a certain projecting height at fixed intervals. At the corners of joining parts 14, 14a... of respective projections or inserts and molds, gap parts 15, 15a... or vertical holes 18, 18a... are provided. In addition, on the inner wall surfaces of forms 24 24a, vertical grooves 26, 26a... are cut at the positions corresponding to horizontal holes 21, 21a.... When a top force 2 is actuated so as to press a bottom force 2a, onto which a tile body Wa is placed, the air left at the joining parts 14, 14a... and the corners 17, 17a... of the projected and recessed parts in a cavity 25 is passed through the gap parts 15, 15a... and, the vertical holes 18, 18a... and the air at the peripheral edges of the tile body Wa is passed through the groove 26, 26a... and the horizontal holes 21, 21a... so as to be respectively discharged through airtight chambers 20, 20a... Accordingly, the tile body Wa is compacted by the pressure of a press so as to produce the projected and recessed parts. Thus, by means of a large number of recessed parts 11, 11a..., honeycomb- like rib 33 is produced on the rear surface of a ceramics product W.