A belt type continuous plate manufacturing apparatus comprising two facing endless belts 1, 1′ and gaskets 7 sandwiched by belt surfaces at their both side edge portions, wherein a polymerizable
raw material is fed into a space surrounded by the facing belt surfaces and the gaskets 7 from its one end, the polymerizable
raw material is solidified together with running of the belts in a heating zone, and the plate
polymer is taken out from the other end, characterized in that three or more upper and lower roll pairs satisfying the following formulae (1) and (2) are placed so that respective axes thereof orthogonally cross the belt running direction, between a
raw material feeding position and a heating
initiation position; and a method of producing a plate
polymer by using it: D / Z≧0.04 (1), 0.30≦D / X≦0.99 (2) [D=outermost
diameter of roll body portion (mm), Z=width of roll body portion (mm), X=distance between axis centers of adjacent upper and lower roll pairs (mm)].