A steel plate for structural pipes or tubes, comprising: a chemical composition that contains, in mass%, C: 0.060 % to 0.100 %, Si: 0.01 % to 0.50 %, Mn: 1.50 % to 2.50 %, Al: 0.080 % or less, Mo: 0.10 % to 0.50 %, Ti: 0.005 % to 0.025 %, Nb: 0.005 % to 0.080 %, N: 0.001 % to 0.010 %, O: 0.0050 % or less, P: 0.010 % or less, S: 0.0010 % or less, optionally V: 0.005 % to 0.100 %, optionally one or more selected from the group consisting of Cu: 0.50 % or less, Ni: 0.50 % or less, Cr: 0.50 % or less, Ca: 0.0005 % to 0.0035 %, REM: 0.0005 % to 0.0100 %, and B: 0.0020 % or less, and the balance consisting of Fe and inevitable impurities, with the chemical composition satisfying a set of conditions including: a ratio Ti/N of the Ti content in mass% to the N content in mass% being 2.5 or more and 4.0 or less; a carbon equivalent C eq as defined by the following Expression being 0.45 or more and 0.50 or lower; X as defined by the following Expression being 0.10 or more and less than 0.30; and Y as defined by the following Expression being 0.15 or more and 0.50 or less: C eq = C + Mn / 6 + Cu + Ni / 15 + Cr + Mo + V / 5 where each element symbol indicates content in mass% of the element in the steel plate and has a value of 0 if the element is not contained in the steel plate, X = C + Mo / 5 / C eq Y = Mo + Ti + Nb + V where represents the content in atomic% of element M in the steel plate and = 0 when the element M is not contained in the steel plate; and a microstructure that contains bainite in an area fraction of 90 % or more and martensite austenite constituent in an area fraction of less than 3.0 %, wherein the steel plate satisfies a set of conditions including: a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a rolling direction TS L being 760 MPa or more; and TS C - TS L being 30 MPa or less in terms of absolute value, where TS C denotes a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a direction orthogonal to the rolling direction. Cu: 0.50 % or less, Ni: 0.50 % or less, Cr: 0.50 % or less, Ca: 0.0005 % to 0.0035 %, REM: 0.0005 % to 0.0100 %, and B: 0.0020 % or less, and a ratio Ti/N of the Ti content in mass% to the N content in mass% being 2.5 or more and 4.0 or less; a carbon equivalent C eq as defined by the following Expression being 0.45 or more and 0.50 or lower; X as defined by the following Expression being 0.10 or more and less than 0.30; and Y as defined by the following Expression being 0.15 or more and 0.50 or less: C eq = C + Mn / 6 + Cu + Ni / 15 + Cr + Mo + V / 5 where each element symbol indicates content in mass% of the element in the steel plate and has a value of 0 if the element is not contained in the steel plate, X = C + Mo / 5 / C eq Y = Mo + Ti + Nb + V where represents the content in atomic% of element M in the steel plate and = 0 when the element M is not contained in the steel plate; and a microstructure that contains bainite in an area fraction of 90 % or more and martensite austenite constituent in an area fraction of less than 3.0 %, wherein the steel plate satisfies a set of conditions including: a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a rolling direction TS L being 760 MPa or more; and TS C - TS L being 30 MPa or less in terms of absolute value, where TS C denotes a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a direction orthogonal to the rolling direction. a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a rolling direction TS L being 760 MPa or more; and TS C - TS L being 30 MPa or less in terms of absolute value, where TS C denotes a tensile strength measured by a tensile test in accordance with JIS Z 2241 in a direction orthogonal to the rolling direction.