To provide a synthetic resin pipe body having required pressure-proof deformation strength and hardly damaging strength, and efficiently manufacturable without reducing production efficiency in manufacture, without locally weakening strength of a corner part of a square cylinder part and particularly strength of both corner parts, without increasing cost of a product due to increased quantity of resin raw materials, without increasing weight.

The pipe body has a pipe wall of alternately arranging a cylindrical part of a cross-sectional substantially square shape and a cylindrical part of a cross-sectional substantially circular shape in the pipe axis direction, and is constituted so that the respective corner parts in the square cylinder part are formed in the shape of narrowing a width in the pipe axis direction as reaching the direction of a corner top part, and is also constituted so that the respective corner parts in the square cylindrical part are formed in a cross-sectional circular arc shape.