Abstract: A belt filter press has a lower and an upper endless filter belt and a lower and an upper endless support belt which support the upper and lower belts in engagement against a lower and upper row of rollers along a press path, respectively, which rows of rollers define therebetween a press slot which is laterally sealed. To effect lateral sealing of the press slot, two additional rows of rollers are disposed on the two opposite sides of either the upper or lower rows of rollers at such an angle that they bend and press the edge of the corresponding upper or lower belts against the other belts.