A fluid treatment device (100) has a first substrate (210), a second substrate (120), and a resin film (130) located between the first substrate (210) and the second substrate (120). On the first substrate (210) are formed a first flow channel (111), a region (214) facing a valve formed at the end of the first flow channel (111), a second flow channel (112), and a barrier wall (215) located between the region (214) facing the valve and the end of the second flow channel (112). On the second substrate (120) is formed a pressure compartment (123). The region (214) facing the valve and the barrier wall (215) face the pressure compartment (123) on opposite sides of a diaphragm (131) of resin film (130).
