The flow channel unit includes: a pair of end flow channels disposed at an inflow port and an outflow port, respectively, and extending along in flow direction; a center flow channel including a pressure receiving portion having a thin film shape and disposed at a position sandwiched between the pair of end flow channels, a distance from an inner peripheral surface of the pressure receiving portion to an outer peripheral surface thereof being shorter than a distance from an inner peripheral surface of the pair of end flow channels to an outer peripheral surface thereof. The pair of end flow channels and the center flow channel are integrally formed of a flexible resin material, and the pressure detection portion is disposed such that the pressure of the fluid circulated through a flow channel is transmitted via the pressure receiving portion.