Seamless steel pipe suitable for use in sour environment

A seamless steel pipe, comprising a base material and a decarburized layer formed on a surface of the base material, wherein

• a chemical composition of the base material consists of, in mass %,
• C:
• 0.20 to 0.50%,
• Si:
• 0.05 to 0.50%,
• Mn:
• 0.01 to 1.00%,
• P:
• 0.0300% or less,
• S:
• 0.0100% or less,
• Al:
• 0.005 to 0.100%,
• Cr:
• 0.30 to 1.20%,
• Mo:
• 0.30 to 1.50%,
• Ti:
• 0.002 to 0.050%,
• V:
• 0.01 to 0.30%,
• Nb:
• 0.002 to 0.100%,
• B:
• 0.0001 to 0.0050%,
• N:
• 0.0100% or less,
• O:
• 0.0050% or less,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• Zr 0 to 0.0100%,
• rare earth metal:
• 0 to 0.0100%,
• Co:
• 0 to 0.50%,
• W:
• 0 to 0.50%,
• Cu:
• 0 to 0.50%,
• Ni:
• 0 to 0.50%, and
• with the balance being Fe and impurities, wherein
• a yield strength of the base material is 655 MPa or more,
• a yield ratio of the base material is 85.0% or more, wherein
• the decarburized layer has a depth of 150 μm or less.