To provide a vent pipe arrangement of an underground tank, which has improved workability.

A vent pipe joint 40 includes a joint body 80, a valve seat member 90 provided at the joint body 80, a valve mechanism 100 that works as an atmospheric valve, an opening 110 formed on a side face of the joint body 80 facing the valve seat member 90, and a lid member 120 that closes the opening 110. The joint body 80 has a partition wall 130 partitioning an internal space into a tank communicating side chamber 86 and an atmosphere communicating side chamber 88, and a through-hole 140 formed in the partition wall 130. The valve mechanism 100 has a first valve element 150 that opens/closes a valve seat 92 of the valve seat member 90, a first coil spring 160 that urges the first valve element 150 in a direction of valve opening, a second valve element 170 that opens/closes a channel 152 of the first valve element 150, a second coil spring 180 that urges the second valve element 170 in a direction of valve opening, and a third valve element 190 that opens/closes a channel 172 of the second valve element 170.