The invention discloses a filter pressure adjusting device applied to a beer saccharifying system. The filter pressure adjusting device comprises a filter container, a first liquidometer, a second liquidometer, a grain raking machine, a collecting system and an adjusting system, wherein a spent grain cavity and a wheat juice collecting cavity are formed in the filter container, a filtering sieve plate is arranged between the spent grain cavity and the wheat juice collecting cavity, the first liquidometer and the second liquidometer are connected with the spent grain cavity and the wheat juice collecting cavity, and a raker of the grain raking machine is arranged in the spent grain cavity; the collecting system comprises a wheat juice guiding-out pipe, a wheat juice collecting pipe, a wheat juice pump, a guiding-out valve and an adjusting valve; the wheat juice collecting cavity, the wheat juice guiding-out pipe, the wheat juice collecting pipe and the wheat juice pump are sequentially connected; the guiding-out valve is arranged on the wheat juice guiding-out pipe, and the adjusting valve is arranged on the wheat juice collecting pipe; the adjusting system comprises an air pipe and an air valve; one end of the air pipe is connected with the wheat juice pump, and the other end of the air pipe is communicated with atmosphere; the air valve is arranged on the air pipe. The device can visually present pressure situations of a spent grain layer and the wheat juice collecting cavity, can effectively balance suction force of the wheat juice pump and improves wheat juice filtering efficiency.