material to expand outwardly in the radial direction upon receiving the liquid pressure at center wall part 341 from first guide channel 23 side at the same time peripheral wall part 342 is rotated about a contact point where peripheral wall part 342 intersects with second plate like part 31 as a rotation axis therefore fourth portion 3431 can be smoothly displaced toward inner bottom surface 3321 of second section 332 thus diaphragm part 34 is formed into a suitable shape to be deformed toward inner bottom surface 3321 upon efficiently receiving the liquid pressure of the irrigation liquid in first guide channel 23 accordingly the channel width can be regulated more properly such an effect can be further enhanced by forming a portion near fourth portion 3431 in diaphragm part 34 to be thinner it is noted that the channel width may be regulated more stably by forming fourth portion 3431 to be further thicker as has been described above according to the present embodiment the dripper includes at least a pipe for penetrating the tube wall of the tube through which the irrigation liquid is supplied a flange part extending outwardly from the outer periphery of that pipe a partition wall that closes the inside of that pipe in that flange part and a bypass channel that is formed inside the flange part and allows communication between two portions of the pipe partitioned by the partition wall and that bypass channel includes a pressure reduction channel for reducing the pressure of the irrigation liquid flowing through the bypass channel in addition the dripper is composed of the above mentioned first member and second member that divide the pipe part and flange part into two portions and the partition wall is integrally formed with either of first.