To ensure high airtightness even in the case of high pressure acting upon the outside rather than the inside of a pipe by specifying the shoulder angle of a torque shoulder part and the lip ratio of a metal seal part of a pin part.

A pipe connecting threaded joint is composed of a pin part 11 and a box part 21, and the pin part 11 and the box part 21 respectively have metal seal parts 13, 23 and torque shoulder parts 14, 24. In this case, the shoulder angle θ of the torque shoulder parts 14, 24 are to be 5-20°, and a lip ratio (S1/DB)/(WT/OD) between the root thickness S1 of a metal seal lip part 17 of the pin part 11 and pipe thickness WT is to be 52% or more, where DB is the inner diameter of the root of the seal lip part 17, and OD is the outer diameter of a pipe. Radial deformation at the time of external pressure acting is thereby prevented, and the deformation of the seal lip part 17 of the pin part 11 to minimum collapse pressure is reduced so as to obtain rigidity required to hold the sealing performance of the metal seal parts.