This electric resistance welded steel pipe comprises a base material part having a predetermined chemical composition and a welded part. If tB is the wall thickness of the base material part and tS is the wall thickness of the welded part, the microstructure of the base material part at a position where the depth from the outer surface is (1/4)tB is composed of, in area%, from 10% to 50% of bainite, from 50% to 90% of polygonal ferrite, and 1% or less of residual structures, while having an average crystal grain size of 20 μm or less; the microstructure of the welded part at a position where the depth from the outer surface is (1/4)tS is composed of, in area%, from 70% to 90% of bainite, polygonal ferrite, and 1% or less of residual structures, while having an average crystal grain size of 15 μm or less. The degree of integration of (001) at the butted surface of the welded part is 1.5 or less; the hardness of the welded part is 250 Hv or less; and at -20°C, the base material part and the welded part have a Charpy impact absorbed energy of 150 J or more, a yield stress of from 360 MPa to 600 MPa, and a tensile strength of from 465 MPa to 760 MPa.