Aiming to achieve both high functionality and flexibility in soft robot system, this paper presents a soft urethane sheet-like valve with an amplifier that can perform logical operations using only pneumatic signals. When the control chamber in the valve is pressurized, the main path is compressed along its central axis, buckling and being pressed,resulting in blockage. This allows control by a pressure signal smaller than that within the main channel. Furthermore, similar to transistors in electrical circuits, when combined, the proposed valve can perform a variety of logical operations. The basic type operates as a NOT logic element, which is named the fluidic sheet transistor (FST). By integrating multiple FSTs, logical operations such as positive logic, NAND, and NOR can be performed on a single sheet. This paper describes the operating principle, fabrication method, and characteristics of the FST,followed by a method for configuring logical operations.Moreover, we demonstrate the construction of a latch circuit(self-holding logic circuit) using FST, introducing a prototype of a fluid robot system that combines a tactile tube as a fluidic detector and fluid actuators. This demonstrates that it is possible to generate behavior that actively changes posture when hitting an obstacle using only air pressure from a single pipe, which verifies the effectiveness of the proposed methods.